diff --git a/README.md b/README.md
index abbf7af..7978030 100644
--- a/README.md
+++ b/README.md
@@ -133,6 +133,8 @@ converter = load_converter("obo", refresh=True)
 
 This will perform a fetch from http://obofoundry.org/registry/obo_prefixes.ttl
 
+prefix.cc is the exception: `refresh=True` still uses the bundled prefix.cc data, because prefix.cc is not curated (see [Refreshing the Data](#refreshing-the-data)).
+
 ## Context Metadata
 
 See [contexts.curated.yaml](src/prefixmaps/data/contexts.curated.yaml)
@@ -172,6 +174,11 @@ The data can be refreshed in several ways:
     make etl
     ```
 
+prefix.cc is not refreshed by default, because it has no curation and spam keeps reappearing there (see [#61](https://github.com/linkml/prefixmaps/issues/61)).
+To fix a semantic web prefix, add it to [linked_data.curated.yaml](https://github.com/linkml/prefixmaps/blob/main/src/prefixmaps/data/linked_data.curated.yaml), which takes precedence over prefix.cc in the merged contexts.
+To download prefix.cc anyway, run `slurp-prefixmaps --refresh-prefixcc`, and review the rows it prints and the resulting CSV diff before committing.
+prefix.cc entries that must never be imported are listed in [prefixcc.excluded.yaml](https://github.com/linkml/prefixmaps/blob/main/src/prefixmaps/data/prefixcc.excluded.yaml).
+
 TODO: make a github action that auto-releases new versions
 
 Note that PRs should *not* be made against the individual CSV files. These are generated from upstream sources.
diff --git a/docs/intro.md b/docs/intro.md
index 5682205..ab3695c 100644
--- a/docs/intro.md
+++ b/docs/intro.md
@@ -126,6 +126,8 @@ ctxt = load_context("obo", refresh=True)
 
 This will perform a fetch from http://obofoundry.org/registry/obo_prefixes.ttl
 
+prefix.cc is the exception: `refresh=True` still uses the bundled prefix.cc data, because prefix.cc is not curated.
+
 ## Context Metadata
 
 See [contexts.curated.yaml](src/prefixmaps/data/contexts.curated.yaml)
@@ -146,6 +148,11 @@ These can be regenerated using:
 make etl
 ```
 
+prefix.cc is not refreshed by default, because it has no curation and spam keeps reappearing there.
+To fix a semantic web prefix, add it to `linked_data.curated.yaml`, which takes precedence over prefix.cc in the merged contexts.
+To download prefix.cc anyway, run `slurp-prefixmaps --refresh-prefixcc`, and review the rows it prints and the resulting CSV diff before committing.
+prefix.cc entries that must never be imported are listed in `prefixcc.excluded.yaml`.
+
 TODO: make a github action that auto-released new versions
 
 ## Requesting new prefixes
diff --git a/src/prefixmaps/data/merged.csv b/src/prefixmaps/data/merged.csv
index da3a25d..6c3de9d 100644
--- a/src/prefixmaps/data/merged.csv
+++ b/src/prefixmaps/data/merged.csv
@@ -936,7 +936,6 @@ merged,BFO,http://www.ebi.ac.uk/ols/ontologies/bfo/terms?iri=http://purl.obolibr
 merged,BFO,https://bioregistry.io/BFO:,prefix_alias,bioregistry
 merged,BFO,https://purl.obolibrary.org/obo/BFO_,prefix_alias,bioregistry
 merged,BFO,https://www.ebi.ac.uk/ols/ontologies/bfo/terms?iri=http://purl.obolibrary.org/obo/BFO_,prefix_alias,bioregistry
-merged,bgcat,http://bg.dbpedia.org/resource/?????????:,canonical,prefixcc
 merged,bgdbp,http://bg.dbpedia.org/property/,canonical,prefixcc
 merged,bgdbr,http://bg.dbpedia.org/resource/,canonical,prefixcc
 merged,BGEE.FAMILY,http://identifiers.org/bgee.family/,canonical,bioregistry
@@ -1972,7 +1971,6 @@ merged,CHEBI,https://www.ebi.ac.uk/chebi/searchId.do?chebiId=,prefix_alias,biore
 merged,CHEBI,https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:,prefix_alias,bioregistry
 merged,CHEBI,https://www.ebi.ac.uk/ols/ontologies/chebi/terms?iri=http://purl.obolibrary.org/obo/CHEBI_,prefix_alias,bioregistry
 merged,CHEBIID,http://purl.obolibrary.org/obo/CHEBI_,namespace_alias,bioregistry
-merged,check,http://pornhub.com/,canonical,prefixcc
 merged,checks,https://data.digichecks.eu/def/,canonical,prefixcc
 merged,CHEMBL,http://identifiers.org/chembl/,canonical,bioregistry
 merged,CHEMBL,http://bio2rdf.org/chembl:,prefix_alias,bioregistry
@@ -3547,7 +3545,6 @@ merged,DHBA,https://bioregistry.io/DHBA:,prefix_alias,bioregistry
 merged,DI,https://www.uniprot.org/diseases/,namespace_alias,bioregistry
 merged,diag,http://www.loc.gov/zing/srw/diagnostic/,canonical,prefixcc
 merged,dicera,http://semweb.mmlab.be/ns/dicera#,canonical,prefixcc
-merged,dick,http://pornhub.com/,namespace_alias,prefixcc
 merged,DICOM,http://dicom.nema.org/resources/ontology/DCM/,canonical,bioregistry
 merged,DICOM,http://bioregistry.io/dicom:,prefix_alias,bioregistry
 merged,DICOM,https://bioregistry.io/dicom:,prefix_alias,bioregistry
@@ -4946,7 +4943,6 @@ merged,FAO.ASFIS,http://www.fao.org/fishery/en/species/,prefix_alias,bioregistry
 merged,FAO.ASFIS,https://bioregistry.io/asfis:,prefix_alias,bioregistry
 merged,FAO.ASFIS,https://bioregistry.io/fao.asfis:,prefix_alias,bioregistry
 merged,faostat,http://reference.eionet.europa.eu/faostat/schema/,canonical,prefixcc
-merged,faptica,https://faptica.com/,canonical,prefixcc
 merged,faq,http://www.openlinksw.com/ontology/faq#,canonical,prefixcc
 merged,FB,http://identifiers.org/flybase/,canonical,go
 merged,FBbi,http://purl.obolibrary.org/obo/FBbi_,canonical,obo
@@ -5261,7 +5257,6 @@ merged,friends,http://www.openarchives.org/OAI/2.0/friends/,canonical,prefixcc
 merged,frir,http://purl.org/twc/ontology/frir.owl#,canonical,prefixcc
 merged,fro,https://foundry.ai.mil/ontology/nas/fro/,canonical,prefixcc
 merged,frsad,http://iflastandards.info/ns/fr/frsad/,canonical,prefixcc
-merged,fs,https://www.compliancequest.com/training-management-software-system-solutions/,canonical,prefixcc
 merged,FSNP,http://identifiers.org/fsnp/,canonical,bioregistry
 merged,FSNP,http://bio2rdf.org/fsnp:,prefix_alias,bioregistry
 merged,FSNP,http://bioregistry.io/fsnp:,prefix_alias,bioregistry
@@ -5279,7 +5274,6 @@ merged,fssp,http://linkeddata.fssprus.ru/resource/,canonical,prefixcc
 merged,ftcontent,http://www.ft.com/ontology/content/,canonical,prefixcc
 merged,fti,http://franz.com/ns/allegrograph/2.2/textindex/,canonical,prefixcc
 merged,ftr,https://w3id.org/ftr#,canonical,prefixcc
-merged,fugas,https://onlyfans.com/sammuwuu/,canonical,prefixcc
 merged,fun,http://w3id.org/sparql-generate/fn/,canonical,prefixcc
 merged,func,http://www.w3.org/2007/rif-builtin-function#,canonical,prefixcc
 merged,FUNCBASE.FLY,http://identifiers.org/funcbase.fly/,canonical,bioregistry
@@ -8049,7 +8043,6 @@ merged,lds,https://solid.ti.rw.fau.de/public/ns/linked-data-structures#,canonica
 merged,ldt,https://www.w3.org/ns/ldt#,canonical,prefixcc
 merged,ldvm,http://linked.opendata.cz/ontology/ldvm/,canonical,prefixcc
 merged,leak,http://maco.com/,canonical,prefixcc
-merged,leaks,https://onlyfans.com/chelxie/,canonical,prefixcc
 merged,led,http://led.kmi.open.ac.uk/term/,canonical,prefixcc
 merged,legal,http://www.w3.org/ns/legal#,canonical,prefixcc
 merged,LEI,http://identifiers.org/lei/,canonical,bioregistry
@@ -8285,7 +8278,6 @@ merged,lis,http://rds.posccaesar.org/ontology/lis14/rdl/,canonical,prefixcc
 merged,list,http://www.w3.org/2000/10/swap/list#,canonical,prefixcc
 merged,literal,http://www.essepuntato.it/2010/06/literalreification/,canonical,prefixcc
 merged,literature,http://purl.org/net/cnyt-literature#,canonical,prefixcc
-merged,ljkl,http://teste.com/,canonical,prefixcc
 merged,ll,http://lodlaundromat.org/resource/,canonical,prefixcc
 merged,llalg,http://www.linklion.org/algorithm/,canonical,prefixcc
 merged,lldr,http://purl.oclc.org/NET/lldr/ns#,canonical,prefixcc
@@ -11152,7 +11144,6 @@ merged,ONE,https://purl.obolibrary.org/obo/ONE_,prefix_alias,bioregistry
 merged,ONE,https://www.ebi.ac.uk/ols/ontologies/one/terms?iri=http://purl.obolibrary.org/obo/ONE_,prefix_alias,bioregistry
 merged,one,https://bioportal.bioontology.org/ontologies/ONE/,prefix_alias,prefixcc
 merged,onisep,http://rdf.onisep.fr/resource/,canonical,prefixcc
-merged,onlyfans,https://cutt.ly/3ry8LMcK/,canonical,prefixcc
 merged,ONS,http://purl.obolibrary.org/obo/ONS_,canonical,obo
 merged,ONS,http://bioregistry.io/ONS:,prefix_alias,bioregistry
 merged,ONS,http://www.ebi.ac.uk/ols/ontologies/ons/terms?iri=http://purl.obolibrary.org/obo/ONS_,prefix_alias,bioregistry
@@ -12774,7 +12765,6 @@ merged,prviv,http://purl.org/net/provenance/integrity#,canonical,prefixcc
 merged,prvr,http://purl.org/ontology/prv/rules#,canonical,prefixcc
 merged,prvt,http://purl.org/net/provenance/types#,namespace_alias,prefixcc
 merged,prvtypes,http://purl.org/net/provenance/types#,canonical,prefixcc
-merged,przecieki,http://onlyfans.com/emiliaszymanska/,canonical,prefixcc
 merged,ps,https://w3id.org/payswarm#,canonical,prefixcc
 merged,PSCDB,http://identifiers.org/pscdb/,canonical,bioregistry
 merged,PSCDB,http://bioregistry.io/pscdb:,prefix_alias,bioregistry
@@ -13091,7 +13081,6 @@ merged,QTLDB,https://www.animalgenome.org/cgi-bin/QTLdb/OA/qdetails?QTL_ID=,pref
 merged,QTLDB,https://www.animalgenome.org/cgi-bin/QTLdb/SS/qdetails?QTL_ID=,prefix_alias,bioregistry
 merged,qu,http://purl.oclc.org/NET/ssnx/qu/qu#,canonical,prefixcc
 merged,quak,http://dev.w3.org/cvsweb/2000/quacken/vocab#,canonical,prefixcc
-merged,qualityze,https://www.qualityze.com/document-management/,canonical,prefixcc
 merged,quantities,http://eulersharp.sourceforge.net/2003/03swap/quantitiesExtension#,canonical,prefixcc
 merged,quantity,http://qudt.org/schema/quantity#,canonical,prefixcc
 merged,qud,http://qudt.org/1.1/schema/qudt#,namespace_alias,prefixcc
@@ -13130,7 +13119,6 @@ merged,railml3,http://ontology.railml.org/railml3#,canonical,prefixcc
 merged,rami,http://iais.fraunhofer.de/vocabs/rami#,canonical,prefixcc
 merged,ramon,http://rdfdata.eionet.europa.eu/ramon/ontology/,canonical,prefixcc
 merged,rank,http://www.ontotext.com/owlim/RDFRank#,canonical,prefixcc
-merged,rankrage,https://rankrage.de/,canonical,prefixcc
 merged,RAPDB.LOCUS,http://identifiers.org/rapdb.locus/,canonical,bioregistry
 merged,RAPDB.LOCUS,http://bioregistry.io/irgsp:,prefix_alias,bioregistry
 merged,RAPDB.LOCUS,http://bioregistry.io/rapdb.locus:,prefix_alias,bioregistry
@@ -14128,7 +14116,6 @@ merged,SEO,http://bioregistry.io/seo:,prefix_alias,bioregistry
 merged,SEO,http://w3id.org/seo#,prefix_alias,bioregistry
 merged,SEO,https://bioregistry.io/seo:,prefix_alias,bioregistry
 merged,seo,http://sda.tech/SEOontology/SEO/,prefix_alias,prefixcc
-merged,seokoeln,http://rankrage.de/,canonical,prefixcc
 merged,SEP,http://purl.obolibrary.org/obo/SEP_,canonical,obo
 merged,SEP,http://bio2rdf.org/sep:,prefix_alias,bioregistry
 merged,SEP,http://bioregistry.io/SEP:,prefix_alias,bioregistry
@@ -15619,7 +15606,6 @@ merged,TXPO,http://www.ebi.ac.uk/ols/ontologies/txpo/terms?iri=http://purl.oboli
 merged,TXPO,https://bioregistry.io/TXPO:,prefix_alias,bioregistry
 merged,TXPO,https://purl.obolibrary.org/obo/TXPO_,prefix_alias,bioregistry
 merged,TXPO,https://www.ebi.ac.uk/ols/ontologies/txpo/terms?iri=http://purl.obolibrary.org/obo/TXPO_,prefix_alias,bioregistry
-merged,type,http://teste.com/teste/,canonical,prefixcc
 merged,tzont,http://www.w3.org/2006/timezone#,canonical,prefixcc
 merged,ub,http://www.lehigh.edu/~zhp2/2004/0401/univ-bench.owl#,canonical,prefixcc
 merged,ubbont,http://data.ub.uib.no/ontology/,canonical,prefixcc
@@ -16374,7 +16360,6 @@ merged,VECTORBASE,https://n2t.net/vectorbase:,prefix_alias,bioregistry
 merged,VECTORBASE,https://vectorbase.org/gene/,prefix_alias,bioregistry
 merged,VECTORBASE,https://vectorbase.org/vectorbase/app/record/gene/,prefix_alias,bioregistry
 merged,VECTORBASE,https://www.vectorbase.org/[?species_name]/Gene/Summary?db=core;g=,prefix_alias,bioregistry
-merged,veelana,http://onlyfans.com/veelana/,canonical,prefixcc
 merged,VEGBANK,http://identifiers.org/vegbank/,canonical,bioregistry
 merged,VEGBANK,http://bioregistry.io/vegbank:,prefix_alias,bioregistry
 merged,VEGBANK,http://identifiers.org/vegbank:,prefix_alias,bioregistry
diff --git a/src/prefixmaps/data/merged.monarch.csv b/src/prefixmaps/data/merged.monarch.csv
index f26861f..b87346c 100644
--- a/src/prefixmaps/data/merged.monarch.csv
+++ b/src/prefixmaps/data/merged.monarch.csv
@@ -936,7 +936,6 @@ merged.monarch,BFO,http://www.ebi.ac.uk/ols/ontologies/bfo/terms?iri=http://purl
 merged.monarch,BFO,https://bioregistry.io/BFO:,prefix_alias,bioregistry
 merged.monarch,BFO,https://purl.obolibrary.org/obo/BFO_,prefix_alias,bioregistry
 merged.monarch,BFO,https://www.ebi.ac.uk/ols/ontologies/bfo/terms?iri=http://purl.obolibrary.org/obo/BFO_,prefix_alias,bioregistry
-merged.monarch,bgcat,http://bg.dbpedia.org/resource/?????????:,canonical,prefixcc
 merged.monarch,bgdbp,http://bg.dbpedia.org/property/,canonical,prefixcc
 merged.monarch,bgdbr,http://bg.dbpedia.org/resource/,canonical,prefixcc
 merged.monarch,BGEE.FAMILY,http://identifiers.org/bgee.family/,canonical,bioregistry
@@ -1972,7 +1971,6 @@ merged.monarch,CHEBI,https://www.ebi.ac.uk/chebi/searchId.do?chebiId=,prefix_ali
 merged.monarch,CHEBI,https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:,prefix_alias,bioregistry
 merged.monarch,CHEBI,https://www.ebi.ac.uk/ols/ontologies/chebi/terms?iri=http://purl.obolibrary.org/obo/CHEBI_,prefix_alias,bioregistry
 merged.monarch,CHEBIID,http://purl.obolibrary.org/obo/CHEBI_,namespace_alias,bioregistry
-merged.monarch,check,http://pornhub.com/,canonical,prefixcc
 merged.monarch,checks,https://data.digichecks.eu/def/,canonical,prefixcc
 merged.monarch,CHEMBL,http://identifiers.org/chembl/,canonical,bioregistry
 merged.monarch,CHEMBL,http://bio2rdf.org/chembl:,prefix_alias,bioregistry
@@ -3547,7 +3545,6 @@ merged.monarch,DHBA,https://bioregistry.io/DHBA:,prefix_alias,bioregistry
 merged.monarch,DI,https://www.uniprot.org/diseases/,namespace_alias,bioregistry
 merged.monarch,diag,http://www.loc.gov/zing/srw/diagnostic/,canonical,prefixcc
 merged.monarch,dicera,http://semweb.mmlab.be/ns/dicera#,canonical,prefixcc
-merged.monarch,dick,http://pornhub.com/,namespace_alias,prefixcc
 merged.monarch,DICOM,http://dicom.nema.org/resources/ontology/DCM/,canonical,bioregistry
 merged.monarch,DICOM,http://bioregistry.io/dicom:,prefix_alias,bioregistry
 merged.monarch,DICOM,https://bioregistry.io/dicom:,prefix_alias,bioregistry
@@ -4946,7 +4943,6 @@ merged.monarch,FAO.ASFIS,http://www.fao.org/fishery/en/species/,prefix_alias,bio
 merged.monarch,FAO.ASFIS,https://bioregistry.io/asfis:,prefix_alias,bioregistry
 merged.monarch,FAO.ASFIS,https://bioregistry.io/fao.asfis:,prefix_alias,bioregistry
 merged.monarch,faostat,http://reference.eionet.europa.eu/faostat/schema/,canonical,prefixcc
-merged.monarch,faptica,https://faptica.com/,canonical,prefixcc
 merged.monarch,faq,http://www.openlinksw.com/ontology/faq#,canonical,prefixcc
 merged.monarch,FB,http://identifiers.org/flybase/,canonical,go
 merged.monarch,FBbi,http://purl.obolibrary.org/obo/FBbi_,canonical,obo
@@ -5261,7 +5257,6 @@ merged.monarch,friends,http://www.openarchives.org/OAI/2.0/friends/,canonical,pr
 merged.monarch,frir,http://purl.org/twc/ontology/frir.owl#,canonical,prefixcc
 merged.monarch,fro,https://foundry.ai.mil/ontology/nas/fro/,canonical,prefixcc
 merged.monarch,frsad,http://iflastandards.info/ns/fr/frsad/,canonical,prefixcc
-merged.monarch,fs,https://www.compliancequest.com/training-management-software-system-solutions/,canonical,prefixcc
 merged.monarch,FSNP,http://identifiers.org/fsnp/,canonical,bioregistry
 merged.monarch,FSNP,http://bio2rdf.org/fsnp:,prefix_alias,bioregistry
 merged.monarch,FSNP,http://bioregistry.io/fsnp:,prefix_alias,bioregistry
@@ -5279,7 +5274,6 @@ merged.monarch,fssp,http://linkeddata.fssprus.ru/resource/,canonical,prefixcc
 merged.monarch,ftcontent,http://www.ft.com/ontology/content/,canonical,prefixcc
 merged.monarch,fti,http://franz.com/ns/allegrograph/2.2/textindex/,canonical,prefixcc
 merged.monarch,ftr,https://w3id.org/ftr#,canonical,prefixcc
-merged.monarch,fugas,https://onlyfans.com/sammuwuu/,canonical,prefixcc
 merged.monarch,fun,http://w3id.org/sparql-generate/fn/,canonical,prefixcc
 merged.monarch,func,http://www.w3.org/2007/rif-builtin-function#,canonical,prefixcc
 merged.monarch,FUNCBASE.FLY,http://identifiers.org/funcbase.fly/,canonical,bioregistry
@@ -8049,7 +8043,6 @@ merged.monarch,lds,https://solid.ti.rw.fau.de/public/ns/linked-data-structures#,
 merged.monarch,ldt,https://www.w3.org/ns/ldt#,canonical,prefixcc
 merged.monarch,ldvm,http://linked.opendata.cz/ontology/ldvm/,canonical,prefixcc
 merged.monarch,leak,http://maco.com/,canonical,prefixcc
-merged.monarch,leaks,https://onlyfans.com/chelxie/,canonical,prefixcc
 merged.monarch,led,http://led.kmi.open.ac.uk/term/,canonical,prefixcc
 merged.monarch,legal,http://www.w3.org/ns/legal#,canonical,prefixcc
 merged.monarch,LEI,http://identifiers.org/lei/,canonical,bioregistry
@@ -8285,7 +8278,6 @@ merged.monarch,lis,http://rds.posccaesar.org/ontology/lis14/rdl/,canonical,prefi
 merged.monarch,list,http://www.w3.org/2000/10/swap/list#,canonical,prefixcc
 merged.monarch,literal,http://www.essepuntato.it/2010/06/literalreification/,canonical,prefixcc
 merged.monarch,literature,http://purl.org/net/cnyt-literature#,canonical,prefixcc
-merged.monarch,ljkl,http://teste.com/,canonical,prefixcc
 merged.monarch,ll,http://lodlaundromat.org/resource/,canonical,prefixcc
 merged.monarch,llalg,http://www.linklion.org/algorithm/,canonical,prefixcc
 merged.monarch,lldr,http://purl.oclc.org/NET/lldr/ns#,canonical,prefixcc
@@ -11152,7 +11144,6 @@ merged.monarch,ONE,https://purl.obolibrary.org/obo/ONE_,prefix_alias,bioregistry
 merged.monarch,ONE,https://www.ebi.ac.uk/ols/ontologies/one/terms?iri=http://purl.obolibrary.org/obo/ONE_,prefix_alias,bioregistry
 merged.monarch,one,https://bioportal.bioontology.org/ontologies/ONE/,prefix_alias,prefixcc
 merged.monarch,onisep,http://rdf.onisep.fr/resource/,canonical,prefixcc
-merged.monarch,onlyfans,https://cutt.ly/3ry8LMcK/,canonical,prefixcc
 merged.monarch,ONS,http://purl.obolibrary.org/obo/ONS_,canonical,obo
 merged.monarch,ONS,http://bioregistry.io/ONS:,prefix_alias,bioregistry
 merged.monarch,ONS,http://www.ebi.ac.uk/ols/ontologies/ons/terms?iri=http://purl.obolibrary.org/obo/ONS_,prefix_alias,bioregistry
@@ -12774,7 +12765,6 @@ merged.monarch,prviv,http://purl.org/net/provenance/integrity#,canonical,prefixc
 merged.monarch,prvr,http://purl.org/ontology/prv/rules#,canonical,prefixcc
 merged.monarch,prvt,http://purl.org/net/provenance/types#,namespace_alias,prefixcc
 merged.monarch,prvtypes,http://purl.org/net/provenance/types#,canonical,prefixcc
-merged.monarch,przecieki,http://onlyfans.com/emiliaszymanska/,canonical,prefixcc
 merged.monarch,ps,https://w3id.org/payswarm#,canonical,prefixcc
 merged.monarch,PSCDB,http://identifiers.org/pscdb/,canonical,bioregistry
 merged.monarch,PSCDB,http://bioregistry.io/pscdb:,prefix_alias,bioregistry
@@ -13091,7 +13081,6 @@ merged.monarch,QTLDB,https://www.animalgenome.org/cgi-bin/QTLdb/OA/qdetails?QTL_
 merged.monarch,QTLDB,https://www.animalgenome.org/cgi-bin/QTLdb/SS/qdetails?QTL_ID=,prefix_alias,bioregistry
 merged.monarch,qu,http://purl.oclc.org/NET/ssnx/qu/qu#,canonical,prefixcc
 merged.monarch,quak,http://dev.w3.org/cvsweb/2000/quacken/vocab#,canonical,prefixcc
-merged.monarch,qualityze,https://www.qualityze.com/document-management/,canonical,prefixcc
 merged.monarch,quantities,http://eulersharp.sourceforge.net/2003/03swap/quantitiesExtension#,canonical,prefixcc
 merged.monarch,quantity,http://qudt.org/schema/quantity#,canonical,prefixcc
 merged.monarch,qud,http://qudt.org/1.1/schema/qudt#,namespace_alias,prefixcc
@@ -13130,7 +13119,6 @@ merged.monarch,railml3,http://ontology.railml.org/railml3#,canonical,prefixcc
 merged.monarch,rami,http://iais.fraunhofer.de/vocabs/rami#,canonical,prefixcc
 merged.monarch,ramon,http://rdfdata.eionet.europa.eu/ramon/ontology/,canonical,prefixcc
 merged.monarch,rank,http://www.ontotext.com/owlim/RDFRank#,canonical,prefixcc
-merged.monarch,rankrage,https://rankrage.de/,canonical,prefixcc
 merged.monarch,RAPDB.LOCUS,http://identifiers.org/rapdb.locus/,canonical,bioregistry
 merged.monarch,RAPDB.LOCUS,http://bioregistry.io/irgsp:,prefix_alias,bioregistry
 merged.monarch,RAPDB.LOCUS,http://bioregistry.io/rapdb.locus:,prefix_alias,bioregistry
@@ -14128,7 +14116,6 @@ merged.monarch,SEO,http://bioregistry.io/seo:,prefix_alias,bioregistry
 merged.monarch,SEO,http://w3id.org/seo#,prefix_alias,bioregistry
 merged.monarch,SEO,https://bioregistry.io/seo:,prefix_alias,bioregistry
 merged.monarch,seo,http://sda.tech/SEOontology/SEO/,prefix_alias,prefixcc
-merged.monarch,seokoeln,http://rankrage.de/,canonical,prefixcc
 merged.monarch,SEP,http://purl.obolibrary.org/obo/SEP_,canonical,obo
 merged.monarch,SEP,http://bio2rdf.org/sep:,prefix_alias,bioregistry
 merged.monarch,SEP,http://bioregistry.io/SEP:,prefix_alias,bioregistry
@@ -15619,7 +15606,6 @@ merged.monarch,TXPO,http://www.ebi.ac.uk/ols/ontologies/txpo/terms?iri=http://pu
 merged.monarch,TXPO,https://bioregistry.io/TXPO:,prefix_alias,bioregistry
 merged.monarch,TXPO,https://purl.obolibrary.org/obo/TXPO_,prefix_alias,bioregistry
 merged.monarch,TXPO,https://www.ebi.ac.uk/ols/ontologies/txpo/terms?iri=http://purl.obolibrary.org/obo/TXPO_,prefix_alias,bioregistry
-merged.monarch,type,http://teste.com/teste/,canonical,prefixcc
 merged.monarch,tzont,http://www.w3.org/2006/timezone#,canonical,prefixcc
 merged.monarch,ub,http://www.lehigh.edu/~zhp2/2004/0401/univ-bench.owl#,canonical,prefixcc
 merged.monarch,ubbont,http://data.ub.uib.no/ontology/,canonical,prefixcc
@@ -16374,7 +16360,6 @@ merged.monarch,VECTORBASE,https://n2t.net/vectorbase:,prefix_alias,bioregistry
 merged.monarch,VECTORBASE,https://vectorbase.org/gene/,prefix_alias,bioregistry
 merged.monarch,VECTORBASE,https://vectorbase.org/vectorbase/app/record/gene/,prefix_alias,bioregistry
 merged.monarch,VECTORBASE,https://www.vectorbase.org/[?species_name]/Gene/Summary?db=core;g=,prefix_alias,bioregistry
-merged.monarch,veelana,http://onlyfans.com/veelana/,canonical,prefixcc
 merged.monarch,VEGBANK,http://identifiers.org/vegbank/,canonical,bioregistry
 merged.monarch,VEGBANK,http://bioregistry.io/vegbank:,prefix_alias,bioregistry
 merged.monarch,VEGBANK,http://identifiers.org/vegbank:,prefix_alias,bioregistry
diff --git a/src/prefixmaps/data/merged.oak.csv b/src/prefixmaps/data/merged.oak.csv
index 74037ed..6a45ae8 100644
--- a/src/prefixmaps/data/merged.oak.csv
+++ b/src/prefixmaps/data/merged.oak.csv
@@ -936,7 +936,6 @@ merged.oak,BFO,http://www.ebi.ac.uk/ols/ontologies/bfo/terms?iri=http://purl.obo
 merged.oak,BFO,https://bioregistry.io/BFO:,prefix_alias,bioregistry
 merged.oak,BFO,https://purl.obolibrary.org/obo/BFO_,prefix_alias,bioregistry
 merged.oak,BFO,https://www.ebi.ac.uk/ols/ontologies/bfo/terms?iri=http://purl.obolibrary.org/obo/BFO_,prefix_alias,bioregistry
-merged.oak,bgcat,http://bg.dbpedia.org/resource/?????????:,canonical,prefixcc
 merged.oak,bgdbp,http://bg.dbpedia.org/property/,canonical,prefixcc
 merged.oak,bgdbr,http://bg.dbpedia.org/resource/,canonical,prefixcc
 merged.oak,BGEE.FAMILY,http://identifiers.org/bgee.family/,canonical,bioregistry
@@ -1972,7 +1971,6 @@ merged.oak,CHEBI,https://www.ebi.ac.uk/chebi/searchId.do?chebiId=,prefix_alias,b
 merged.oak,CHEBI,https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:,prefix_alias,bioregistry
 merged.oak,CHEBI,https://www.ebi.ac.uk/ols/ontologies/chebi/terms?iri=http://purl.obolibrary.org/obo/CHEBI_,prefix_alias,bioregistry
 merged.oak,CHEBIID,http://purl.obolibrary.org/obo/CHEBI_,namespace_alias,bioregistry
-merged.oak,check,http://pornhub.com/,canonical,prefixcc
 merged.oak,checks,https://data.digichecks.eu/def/,canonical,prefixcc
 merged.oak,CHEMBL,http://identifiers.org/chembl/,canonical,bioregistry
 merged.oak,CHEMBL,http://bio2rdf.org/chembl:,prefix_alias,bioregistry
@@ -3547,7 +3545,6 @@ merged.oak,DHBA,https://bioregistry.io/DHBA:,prefix_alias,bioregistry
 merged.oak,DI,https://www.uniprot.org/diseases/,namespace_alias,bioregistry
 merged.oak,diag,http://www.loc.gov/zing/srw/diagnostic/,canonical,prefixcc
 merged.oak,dicera,http://semweb.mmlab.be/ns/dicera#,canonical,prefixcc
-merged.oak,dick,http://pornhub.com/,namespace_alias,prefixcc
 merged.oak,DICOM,http://dicom.nema.org/resources/ontology/DCM/,canonical,bioregistry
 merged.oak,DICOM,http://bioregistry.io/dicom:,prefix_alias,bioregistry
 merged.oak,DICOM,https://bioregistry.io/dicom:,prefix_alias,bioregistry
@@ -4946,7 +4943,6 @@ merged.oak,FAO.ASFIS,http://www.fao.org/fishery/en/species/,prefix_alias,bioregi
 merged.oak,FAO.ASFIS,https://bioregistry.io/asfis:,prefix_alias,bioregistry
 merged.oak,FAO.ASFIS,https://bioregistry.io/fao.asfis:,prefix_alias,bioregistry
 merged.oak,faostat,http://reference.eionet.europa.eu/faostat/schema/,canonical,prefixcc
-merged.oak,faptica,https://faptica.com/,canonical,prefixcc
 merged.oak,faq,http://www.openlinksw.com/ontology/faq#,canonical,prefixcc
 merged.oak,FB,http://identifiers.org/flybase/,canonical,go
 merged.oak,FBbi,http://purl.obolibrary.org/obo/FBbi_,canonical,obo
@@ -5261,7 +5257,6 @@ merged.oak,friends,http://www.openarchives.org/OAI/2.0/friends/,canonical,prefix
 merged.oak,frir,http://purl.org/twc/ontology/frir.owl#,canonical,prefixcc
 merged.oak,fro,https://foundry.ai.mil/ontology/nas/fro/,canonical,prefixcc
 merged.oak,frsad,http://iflastandards.info/ns/fr/frsad/,canonical,prefixcc
-merged.oak,fs,https://www.compliancequest.com/training-management-software-system-solutions/,canonical,prefixcc
 merged.oak,FSNP,http://identifiers.org/fsnp/,canonical,bioregistry
 merged.oak,FSNP,http://bio2rdf.org/fsnp:,prefix_alias,bioregistry
 merged.oak,FSNP,http://bioregistry.io/fsnp:,prefix_alias,bioregistry
@@ -5279,7 +5274,6 @@ merged.oak,fssp,http://linkeddata.fssprus.ru/resource/,canonical,prefixcc
 merged.oak,ftcontent,http://www.ft.com/ontology/content/,canonical,prefixcc
 merged.oak,fti,http://franz.com/ns/allegrograph/2.2/textindex/,canonical,prefixcc
 merged.oak,ftr,https://w3id.org/ftr#,canonical,prefixcc
-merged.oak,fugas,https://onlyfans.com/sammuwuu/,canonical,prefixcc
 merged.oak,fun,http://w3id.org/sparql-generate/fn/,canonical,prefixcc
 merged.oak,func,http://www.w3.org/2007/rif-builtin-function#,canonical,prefixcc
 merged.oak,FUNCBASE.FLY,http://identifiers.org/funcbase.fly/,canonical,bioregistry
@@ -8049,7 +8043,6 @@ merged.oak,lds,https://solid.ti.rw.fau.de/public/ns/linked-data-structures#,cano
 merged.oak,ldt,https://www.w3.org/ns/ldt#,canonical,prefixcc
 merged.oak,ldvm,http://linked.opendata.cz/ontology/ldvm/,canonical,prefixcc
 merged.oak,leak,http://maco.com/,canonical,prefixcc
-merged.oak,leaks,https://onlyfans.com/chelxie/,canonical,prefixcc
 merged.oak,led,http://led.kmi.open.ac.uk/term/,canonical,prefixcc
 merged.oak,legal,http://www.w3.org/ns/legal#,canonical,prefixcc
 merged.oak,LEI,http://identifiers.org/lei/,canonical,bioregistry
@@ -8285,7 +8278,6 @@ merged.oak,lis,http://rds.posccaesar.org/ontology/lis14/rdl/,canonical,prefixcc
 merged.oak,list,http://www.w3.org/2000/10/swap/list#,canonical,prefixcc
 merged.oak,literal,http://www.essepuntato.it/2010/06/literalreification/,canonical,prefixcc
 merged.oak,literature,http://purl.org/net/cnyt-literature#,canonical,prefixcc
-merged.oak,ljkl,http://teste.com/,canonical,prefixcc
 merged.oak,ll,http://lodlaundromat.org/resource/,canonical,prefixcc
 merged.oak,llalg,http://www.linklion.org/algorithm/,canonical,prefixcc
 merged.oak,lldr,http://purl.oclc.org/NET/lldr/ns#,canonical,prefixcc
@@ -11152,7 +11144,6 @@ merged.oak,ONE,https://purl.obolibrary.org/obo/ONE_,prefix_alias,bioregistry
 merged.oak,ONE,https://www.ebi.ac.uk/ols/ontologies/one/terms?iri=http://purl.obolibrary.org/obo/ONE_,prefix_alias,bioregistry
 merged.oak,one,https://bioportal.bioontology.org/ontologies/ONE/,prefix_alias,prefixcc
 merged.oak,onisep,http://rdf.onisep.fr/resource/,canonical,prefixcc
-merged.oak,onlyfans,https://cutt.ly/3ry8LMcK/,canonical,prefixcc
 merged.oak,ONS,http://purl.obolibrary.org/obo/ONS_,canonical,obo
 merged.oak,ONS,http://bioregistry.io/ONS:,prefix_alias,bioregistry
 merged.oak,ONS,http://www.ebi.ac.uk/ols/ontologies/ons/terms?iri=http://purl.obolibrary.org/obo/ONS_,prefix_alias,bioregistry
@@ -12774,7 +12765,6 @@ merged.oak,prviv,http://purl.org/net/provenance/integrity#,canonical,prefixcc
 merged.oak,prvr,http://purl.org/ontology/prv/rules#,canonical,prefixcc
 merged.oak,prvt,http://purl.org/net/provenance/types#,namespace_alias,prefixcc
 merged.oak,prvtypes,http://purl.org/net/provenance/types#,canonical,prefixcc
-merged.oak,przecieki,http://onlyfans.com/emiliaszymanska/,canonical,prefixcc
 merged.oak,ps,https://w3id.org/payswarm#,canonical,prefixcc
 merged.oak,PSCDB,http://identifiers.org/pscdb/,canonical,bioregistry
 merged.oak,PSCDB,http://bioregistry.io/pscdb:,prefix_alias,bioregistry
@@ -13091,7 +13081,6 @@ merged.oak,QTLDB,https://www.animalgenome.org/cgi-bin/QTLdb/OA/qdetails?QTL_ID=,
 merged.oak,QTLDB,https://www.animalgenome.org/cgi-bin/QTLdb/SS/qdetails?QTL_ID=,prefix_alias,bioregistry
 merged.oak,qu,http://purl.oclc.org/NET/ssnx/qu/qu#,canonical,prefixcc
 merged.oak,quak,http://dev.w3.org/cvsweb/2000/quacken/vocab#,canonical,prefixcc
-merged.oak,qualityze,https://www.qualityze.com/document-management/,canonical,prefixcc
 merged.oak,quantities,http://eulersharp.sourceforge.net/2003/03swap/quantitiesExtension#,canonical,prefixcc
 merged.oak,quantity,http://qudt.org/schema/quantity#,canonical,prefixcc
 merged.oak,qud,http://qudt.org/1.1/schema/qudt#,namespace_alias,prefixcc
@@ -13130,7 +13119,6 @@ merged.oak,railml3,http://ontology.railml.org/railml3#,canonical,prefixcc
 merged.oak,rami,http://iais.fraunhofer.de/vocabs/rami#,canonical,prefixcc
 merged.oak,ramon,http://rdfdata.eionet.europa.eu/ramon/ontology/,canonical,prefixcc
 merged.oak,rank,http://www.ontotext.com/owlim/RDFRank#,canonical,prefixcc
-merged.oak,rankrage,https://rankrage.de/,canonical,prefixcc
 merged.oak,RAPDB.LOCUS,http://identifiers.org/rapdb.locus/,canonical,bioregistry
 merged.oak,RAPDB.LOCUS,http://bioregistry.io/irgsp:,prefix_alias,bioregistry
 merged.oak,RAPDB.LOCUS,http://bioregistry.io/rapdb.locus:,prefix_alias,bioregistry
@@ -14128,7 +14116,6 @@ merged.oak,SEO,http://bioregistry.io/seo:,prefix_alias,bioregistry
 merged.oak,SEO,http://w3id.org/seo#,prefix_alias,bioregistry
 merged.oak,SEO,https://bioregistry.io/seo:,prefix_alias,bioregistry
 merged.oak,seo,http://sda.tech/SEOontology/SEO/,prefix_alias,prefixcc
-merged.oak,seokoeln,http://rankrage.de/,canonical,prefixcc
 merged.oak,SEP,http://purl.obolibrary.org/obo/SEP_,canonical,obo
 merged.oak,SEP,http://bio2rdf.org/sep:,prefix_alias,bioregistry
 merged.oak,SEP,http://bioregistry.io/SEP:,prefix_alias,bioregistry
@@ -15619,7 +15606,6 @@ merged.oak,TXPO,http://www.ebi.ac.uk/ols/ontologies/txpo/terms?iri=http://purl.o
 merged.oak,TXPO,https://bioregistry.io/TXPO:,prefix_alias,bioregistry
 merged.oak,TXPO,https://purl.obolibrary.org/obo/TXPO_,prefix_alias,bioregistry
 merged.oak,TXPO,https://www.ebi.ac.uk/ols/ontologies/txpo/terms?iri=http://purl.obolibrary.org/obo/TXPO_,prefix_alias,bioregistry
-merged.oak,type,http://teste.com/teste/,canonical,prefixcc
 merged.oak,tzont,http://www.w3.org/2006/timezone#,canonical,prefixcc
 merged.oak,ub,http://www.lehigh.edu/~zhp2/2004/0401/univ-bench.owl#,canonical,prefixcc
 merged.oak,ubbont,http://data.ub.uib.no/ontology/,canonical,prefixcc
@@ -16374,7 +16360,6 @@ merged.oak,VECTORBASE,https://n2t.net/vectorbase:,prefix_alias,bioregistry
 merged.oak,VECTORBASE,https://vectorbase.org/gene/,prefix_alias,bioregistry
 merged.oak,VECTORBASE,https://vectorbase.org/vectorbase/app/record/gene/,prefix_alias,bioregistry
 merged.oak,VECTORBASE,https://www.vectorbase.org/[?species_name]/Gene/Summary?db=core;g=,prefix_alias,bioregistry
-merged.oak,veelana,http://onlyfans.com/veelana/,canonical,prefixcc
 merged.oak,VEGBANK,http://identifiers.org/vegbank/,canonical,bioregistry
 merged.oak,VEGBANK,http://bioregistry.io/vegbank:,prefix_alias,bioregistry
 merged.oak,VEGBANK,http://identifiers.org/vegbank:,prefix_alias,bioregistry
diff --git a/src/prefixmaps/data/prefixcc.csv b/src/prefixmaps/data/prefixcc.csv
index b7bb501..a1ce605 100644
--- a/src/prefixmaps/data/prefixcc.csv
+++ b/src/prefixmaps/data/prefixcc.csv
@@ -207,7 +207,6 @@ prefixcc,bevon,http://rdfs.co/bevon/,canonical
 prefixcc,bf,http://id.loc.gov/ontologies/bibframe/,canonical
 prefixcc,bflc,http://id.loc.gov/ontologies/bflc/,canonical
 prefixcc,bfo,http://purl.obolibrary.org/obo/,namespace_alias
-prefixcc,bgcat,http://bg.dbpedia.org/resource/?????????:,canonical
 prefixcc,bgdbp,http://bg.dbpedia.org/property/,canonical
 prefixcc,bgdbr,http://bg.dbpedia.org/resource/,canonical
 prefixcc,bgn,http://bibliograph.net/schemas/,canonical
@@ -364,7 +363,6 @@ prefixcc,ch,https://schema.ld.admin.ch/,canonical
 prefixcc,chameo,https://w3id.org/emmo/domain/characterisation-methodology/chameo#,canonical
 prefixcc,changeset,http://purl.org/vocab/changeset/schema#,namespace_alias
 prefixcc,chear,http://hadatac.org/ont/chear#,canonical
-prefixcc,check,http://pornhub.com/,canonical
 prefixcc,checks,https://data.digichecks.eu/def/,canonical
 prefixcc,chembl,http://rdf.ebi.ac.uk/terms/chembl#,canonical
 prefixcc,cheminf,http://www.semanticweb.org/ontologies/cheminf.owl#,canonical
@@ -667,7 +665,6 @@ prefixcc,dgfr,http://colin.maudry.com/ontologies/dgfr#,canonical
 prefixcc,dgtwc,http://data-gov.tw.rpi.edu/2009/data-gov-twc.rdf#,canonical
 prefixcc,diag,http://www.loc.gov/zing/srw/diagnostic/,canonical
 prefixcc,dicera,http://semweb.mmlab.be/ns/dicera#,canonical
-prefixcc,dick,http://pornhub.com/,namespace_alias
 prefixcc,dicom,http://purl.org/healthcarevocab/v1#,canonical
 prefixcc,dictionary,https://standards.buildingsmart.org/DataDictionary/,canonical
 prefixcc,did,https://w3id.org/dob/id/,canonical
@@ -945,7 +942,6 @@ prefixcc,faldo,http://biohackathon.org/resource/faldo#,canonical
 prefixcc,fam,http://vocab.fusepool.info/fam#,canonical
 prefixcc,fao,http://fao.270a.info/dataset/,canonical
 prefixcc,faostat,http://reference.eionet.europa.eu/faostat/schema/,canonical
-prefixcc,faptica,https://faptica.com/,canonical
 prefixcc,faq,http://www.openlinksw.com/ontology/faq#,canonical
 prefixcc,fbbi,http://purl.obolibrary.org/obo/FBbi_,canonical
 prefixcc,fbbt,http://purl.obolibrary.org/obo/FBbt_,canonical
@@ -1037,13 +1033,11 @@ prefixcc,friends,http://www.openarchives.org/OAI/2.0/friends/,canonical
 prefixcc,frir,http://purl.org/twc/ontology/frir.owl#,canonical
 prefixcc,fro,https://foundry.ai.mil/ontology/nas/fro/,canonical
 prefixcc,frsad,http://iflastandards.info/ns/fr/frsad/,canonical
-prefixcc,fs,https://www.compliancequest.com/training-management-software-system-solutions/,canonical
 prefixcc,fso,https://w3id.org/fso#,canonical
 prefixcc,fssp,http://linkeddata.fssprus.ru/resource/,canonical
 prefixcc,ftcontent,http://www.ft.com/ontology/content/,canonical
 prefixcc,fti,http://franz.com/ns/allegrograph/2.2/textindex/,canonical
 prefixcc,ftr,https://w3id.org/ftr#,canonical
-prefixcc,fugas,https://onlyfans.com/sammuwuu/,canonical
 prefixcc,fun,http://w3id.org/sparql-generate/fn/,canonical
 prefixcc,func,http://www.w3.org/2007/rif-builtin-function#,canonical
 prefixcc,fuseki,http://jena.apache.org/fuseki#,canonical
@@ -1466,7 +1460,6 @@ prefixcc,lds,https://solid.ti.rw.fau.de/public/ns/linked-data-structures#,canoni
 prefixcc,ldt,https://www.w3.org/ns/ldt#,canonical
 prefixcc,ldvm,http://linked.opendata.cz/ontology/ldvm/,canonical
 prefixcc,leak,http://maco.com/,canonical
-prefixcc,leaks,https://onlyfans.com/chelxie/,canonical
 prefixcc,led,http://led.kmi.open.ac.uk/term/,canonical
 prefixcc,legal,http://www.w3.org/ns/legal#,canonical
 prefixcc,lemon,http://lemon-model.net/lemon#,canonical
@@ -1522,7 +1515,6 @@ prefixcc,lis,http://rds.posccaesar.org/ontology/lis14/rdl/,canonical
 prefixcc,list,http://www.w3.org/2000/10/swap/list#,canonical
 prefixcc,literal,http://www.essepuntato.it/2010/06/literalreification/,canonical
 prefixcc,literature,http://purl.org/net/cnyt-literature#,canonical
-prefixcc,ljkl,http://teste.com/,canonical
 prefixcc,ll,http://lodlaundromat.org/resource/,canonical
 prefixcc,llalg,http://www.linklion.org/algorithm/,canonical
 prefixcc,lldr,http://purl.oclc.org/NET/lldr/ns#,canonical
@@ -1994,7 +1986,6 @@ prefixcc,onc,http://www.ics.forth.gr/isl/oncm/core#,canonical
 prefixcc,ondc,http://www.semanticweb.org/ontologies/2012/1/Ontology1329913965202.owl#,canonical
 prefixcc,one,https://bioportal.bioontology.org/ontologies/ONE/,canonical
 prefixcc,onisep,http://rdf.onisep.fr/resource/,canonical
-prefixcc,onlyfans,https://cutt.ly/3ry8LMcK/,canonical
 prefixcc,ons,http://purl.obolibrary.org/obo/ONS_,canonical
 prefixcc,onssprel,http://www.ordnancesurvey.co.uk/ontology/SpatialRelations/v0.2/SpatialRelations.owl#,canonical
 prefixcc,onto,http://www.ontotext.com/,canonical
@@ -2309,7 +2300,6 @@ prefixcc,prviv,http://purl.org/net/provenance/integrity#,canonical
 prefixcc,prvr,http://purl.org/ontology/prv/rules#,canonical
 prefixcc,prvt,http://purl.org/net/provenance/types#,namespace_alias
 prefixcc,prvtypes,http://purl.org/net/provenance/types#,canonical
-prefixcc,przecieki,http://onlyfans.com/emiliaszymanska/,canonical
 prefixcc,ps,https://w3id.org/payswarm#,canonical
 prefixcc,psdo,http://purl.obolibrary.org/obo/PSDO_,canonical
 prefixcc,psh,http://ns.inria.fr/probabilistic-shacl/,canonical
@@ -2349,7 +2339,6 @@ prefixcc,qms,http://data.europa.eu/esco/qms#,canonical
 prefixcc,qrl,http://www.aifb.kit.edu/project/ld-retriever/qrl#,canonical
 prefixcc,qu,http://purl.oclc.org/NET/ssnx/qu/qu#,canonical
 prefixcc,quak,http://dev.w3.org/cvsweb/2000/quacken/vocab#,canonical
-prefixcc,qualityze,https://www.qualityze.com/document-management/,canonical
 prefixcc,quantities,http://eulersharp.sourceforge.net/2003/03swap/quantitiesExtension#,canonical
 prefixcc,quantity,http://qudt.org/schema/quantity#,canonical
 prefixcc,qud,http://qudt.org/1.1/schema/qudt#,canonical
@@ -2374,7 +2363,6 @@ prefixcc,railml3,http://ontology.railml.org/railml3#,canonical
 prefixcc,rami,http://iais.fraunhofer.de/vocabs/rami#,canonical
 prefixcc,ramon,http://rdfdata.eionet.europa.eu/ramon/ontology/,canonical
 prefixcc,rank,http://www.ontotext.com/owlim/RDFRank#,canonical
-prefixcc,rankrage,https://rankrage.de/,canonical
 prefixcc,rating,http://www.tvblob.com/ratings/#,canonical
 prefixcc,raul,http://vocab.deri.ie/raul#,canonical
 prefixcc,raum,https://terminology.fraunhofer.de/voc/raum#,canonical
@@ -2692,7 +2680,6 @@ prefixcc,semts,https://w3id.org/semts/ontology#,canonical
 prefixcc,semtweet,http://semantictweet.com/,canonical
 prefixcc,sense,https://w3id.org/sense#,canonical
 prefixcc,seo,http://sda.tech/SEOontology/SEO/,canonical
-prefixcc,seokoeln,http://rankrage.de/,canonical
 prefixcc,sep,http://purl.obolibrary.org/obo/ZP_,namespace_alias
 prefixcc,sepio,http://purl.obolibrary.org/obo/SEPIO_,canonical
 prefixcc,seq,http://www.ontologydesignpatterns.org/cp/owl/sequence.owl#,canonical
@@ -3221,7 +3208,6 @@ prefixcc,twitter,http://stocktwits.com/,canonical
 prefixcc,tx,http://swtmp.gitlab.io/vocabulary/templates.owl#,canonical
 prefixcc,txn,http://lod.taxonconcept.org/ontology/txn.owl#,canonical
 prefixcc,txpo,http://purl.obolibrary.org/obo/ZP_,namespace_alias
-prefixcc,type,http://teste.com/teste/,canonical
 prefixcc,tzont,http://www.w3.org/2006/timezone#,canonical
 prefixcc,ub,http://www.lehigh.edu/~zhp2/2004/0401/univ-bench.owl#,canonical
 prefixcc,ubbont,http://data.ub.uib.no/ontology/,canonical
@@ -3284,7 +3270,6 @@ prefixcc,vcard2006,http://www.w3.org/2006/vcard/ns#,namespace_alias
 prefixcc,vcardx,http://buzzword.org.uk/rdf/vcardx#,canonical
 prefixcc,vcs,https://data.vlaanderen.be/ns/chemische_stof#,canonical
 prefixcc,vdpp,http://data.lirmm.fr/ontologies/vdpp#,canonical
-prefixcc,veelana,http://onlyfans.com/veelana/,canonical
 prefixcc,vehma,http://deductions.github.io/vehicule-management.owl.ttl#,canonical
 prefixcc,vehman,http://deductions.github.io/vehicule-management.owl.ttl#,namespace_alias
 prefixcc,veo,http://linkeddata.finki.ukim.mk/lod/ontology/veo#,canonical
diff --git a/src/prefixmaps/data/prefixcc.excluded.yaml b/src/prefixmaps/data/prefixcc.excluded.yaml
new file mode 100644
index 0000000..8d4dcf0
--- /dev/null
+++ b/src/prefixmaps/data/prefixcc.excluded.yaml
@@ -0,0 +1,22 @@
+# prefix.cc entries that are never imported, because they are spam or broken.
+#
+# prefix.cc has no curation and spam keeps reappearing there, see
+# https://github.com/linkml/prefixmaps/issues/61 and https://github.com/cygri/prefix.cc/issues/42
+# tests/test_core/test_prefixcc_exclusions.py checks that no bundled context contains them.
+
+# Namespaces on these hosts, or on their subdomains, are dropped.
+hosts:
+  compliancequest.com: software product page, not a vocabulary
+  cuzin.com: spam
+  cutt.ly: URL shortener used for spam
+  faptica.com: spam
+  onlyfans.com: spam
+  pornhub.com: spam
+  qualityze.com: spam, see https://github.com/cygri/prefix.cc/issues/42
+  rankrage.de: SEO agency spam
+  teste.com: placeholder test entries
+
+# These prefixes are dropped, whatever their namespace.
+prefixes:
+  bgcat: namespace corrupted upstream (its Cyrillic characters are replaced by "?")
+  leaks: only ever used for spam, see https://github.com/cygri/prefix.cc/issues/42
diff --git a/src/prefixmaps/ingest/etl_runner.py b/src/prefixmaps/ingest/etl_runner.py
index b8311d9..16444cc 100644
--- a/src/prefixmaps/ingest/etl_runner.py
+++ b/src/prefixmaps/ingest/etl_runner.py
@@ -13,7 +13,7 @@
     from_bioregistry_upper,
 )
 from prefixmaps.ingest.ingest_go import parse_go_xrefs_from_remote
-from prefixmaps.ingest.ingest_jsonld import from_prefixcc
+from prefixmaps.ingest.ingest_jsonld import from_prefixcc, from_prefixcc_snapshot
 from prefixmaps.ingest.ingest_linkml import from_semweb_curated
 from prefixmaps.ingest.ingest_shacl import from_obo
 from prefixmaps.ingest.ingest_w3id import from_w3id
@@ -27,10 +27,13 @@
     "bioportal": from_bioportal_file,
     "bioregistry.upper": from_bioregistry_upper,
     "bioregistry": from_bioregistry,
-    "prefixcc": from_prefixcc,
+    "prefixcc": from_prefixcc_snapshot,
     "w3id": from_w3id,
 }
-"""Maps the name of a context to the python function that can generate it"""
+"""Maps the name of a context to the python function that can generate it.
+
+prefix.cc is frozen, see https://github.com/linkml/prefixmaps/issues/61. Pass
+``refresh_prefixcc=True`` to :func:`run_etl` to download it again."""
 
 COMBINED = {
     "merged": ["obo", "go", "linked_data", "bioregistry.upper", "prefixcc"],
@@ -49,6 +52,8 @@ def load_context_from_source(context: CONTEXT) -> Context:
     - An atomic context (e.g. obo, linked_data)
     - A conbined context (which remixes existing contexts)
 
+    prefix.cc is the exception: it comes from the bundled snapshot, see :data:`CONTEXTS`.
+
     :param context: unique handle of the context
     :return:
     """
@@ -63,14 +68,16 @@ def load_context_from_source(context: CONTEXT) -> Context:
         raise ValueError(f"No such context: {context}")
 
 
-def run_etl(output_directory: Union[str, Path]) -> None:
+def run_etl(output_directory: Union[str, Path], refresh_prefixcc: bool = False) -> None:
     """
     Runs the complete ETL pipeline.
 
-    All contexts are refreshed from upstream sources, and written to the output directory,
-    as CSV.
+    All contexts except prefix.cc are refreshed from upstream sources, and written to the
+    output directory, as CSV.
 
     :param output_directory:
+    :param refresh_prefixcc: if True, also download prefix.cc and print what changed.
+        prefix.cc has no curation, so review those changes before committing them.
     :return:
     """
     # contexts = load_contexts_meta()
@@ -81,6 +88,10 @@ def run_etl(output_directory: Union[str, Path]) -> None:
     contexts: Dict[str, Context] = {
         name: context_getter() for name, context_getter in CONTEXTS.items()
     }
+    if refresh_prefixcc:
+        snapshot = contexts["prefixcc"]
+        contexts["prefixcc"] = from_prefixcc()
+        echo_changes(snapshot, contexts["prefixcc"])
 
     # Create merged contexts
     for merged_name, names in COMBINED.items():
@@ -95,6 +106,21 @@ def run_etl(output_directory: Union[str, Path]) -> None:
             context_to_file(context, file, include_expansion_source=context.name in COMBINED)
 
 
+def echo_changes(old: Context, new: Context) -> None:
+    """
+    Prints the prefix expansions that were added (+) or removed (-) between two versions of a
+    context. Changes that this causes in merged contexts only show up in their CSV diffs.
+
+    :param old:
+    :param new:
+    :return:
+    """
+    old_rows = {(pe.prefix, pe.namespace, pe.status.value) for pe in old.prefix_expansions}
+    new_rows = {(pe.prefix, pe.namespace, pe.status.value) for pe in new.prefix_expansions}
+    for row in sorted(old_rows ^ new_rows, key=lambda row: (row[0].casefold(), row)):
+        click.echo(f"{'+' if row in new_rows else '-'} {new.name} {' '.join(row)}")
+
+
 @click.command
 @click.option(
     "-d",
@@ -103,8 +129,13 @@ def run_etl(output_directory: Union[str, Path]) -> None:
     type=Path,
     help="Path to directory where CSVs are stored",
 )
-def cli(output_directory):
-    run_etl(output_directory)
+@click.option(
+    "--refresh-prefixcc",
+    is_flag=True,
+    help="Also download prefix.cc, which is uncurated, and print what changed for review",
+)
+def cli(output_directory, refresh_prefixcc):
+    run_etl(output_directory, refresh_prefixcc=refresh_prefixcc)
 
 
 if __name__ == "__main__":
diff --git a/src/prefixmaps/ingest/ingest_jsonld.py b/src/prefixmaps/ingest/ingest_jsonld.py
index bb424b6..a479250 100644
--- a/src/prefixmaps/ingest/ingest_jsonld.py
+++ b/src/prefixmaps/ingest/ingest_jsonld.py
@@ -1,14 +1,21 @@
 """Generic JSON-LD ingests."""
 
 import json
-from typing import Any, Dict, List, Optional, TextIO, Union
+from pathlib import Path
+from typing import Any, Dict, List, Mapping, Optional, TextIO, Union
+from urllib.parse import urlparse
 
 import requests
+import yaml
 
+from prefixmaps.data import data_path
 from prefixmaps.datamodel.context import Context
+from prefixmaps.io.parser import load_context
 
 AT_CONTEXT = "@context"
 
+PREFIXCC_URL = "http://prefix.cc/context.jsonld"
+
 PREFIXCC_EXCLUDE = [
     "bp",
     "terms",
@@ -109,6 +116,88 @@ def from_prefixcc() -> Context:
     Longer term we should focus on the curated linked_data.yaml file, and
     moving this to bioregistry.
 
+    Spam and broken entries listed in prefixcc.excluded.yaml are dropped.
+
     :return:
     """
-    return from_jsonld_context_url("http://prefix.cc/context.jsonld", "prefixcc", PREFIXCC_EXCLUDE)
+    exclusions = load_prefixcc_exclusions()
+    jsonld_context = requests.get(url=PREFIXCC_URL).json()
+    if AT_CONTEXT in jsonld_context:
+        jsonld_context[AT_CONTEXT] = {
+            prefix: namespace
+            for prefix, namespace in jsonld_context[AT_CONTEXT].items()
+            if not (
+                isinstance(namespace, str)
+                and is_excluded_from_prefixcc(prefix, namespace, exclusions)
+            )
+        }
+    return from_jsonld_context(jsonld_context, "prefixcc", PREFIXCC_EXCLUDE)
+
+
+def from_prefixcc_snapshot() -> Context:
+    """
+    Loads the prefix.cc snapshot bundled with this package.
+
+    prefix.cc has no curation, so it is not refreshed by default, see
+    https://github.com/linkml/prefixmaps/issues/61. To fix a semweb prefix, add it to
+    linked_data.curated.yaml, which takes precedence over prefix.cc in merged contexts.
+
+    Entries listed in prefixcc.excluded.yaml are still dropped, so a new exclusion takes
+    effect on the next ETL run. Canonical expansions come first, so that merging the
+    snapshot gives the same statuses as merging a fresh download. That relies on prefix.cc
+    having no prefix aliases, which holds because its prefixes are unique and lowercase.
+
+    :return:
+    """
+    exclusions = load_prefixcc_exclusions()
+    context = load_context("prefixcc")
+    context.prefix_expansions = sorted(
+        (
+            pe
+            for pe in context.prefix_expansions
+            if not is_excluded_from_prefixcc(pe.prefix, pe.namespace, exclusions)
+        ),
+        key=lambda pe: not pe.canonical(),
+    )
+    return context
+
+
+def load_prefixcc_exclusions(
+    path: Path = data_path / "prefixcc.excluded.yaml",
+) -> Mapping[str, Mapping[str, str]]:
+    """
+    Loads the prefix.cc entries that are never imported.
+
+    :param path: the exclusions file
+    :return: the excluded ``hosts`` and ``prefixes``, each mapped to the reason
+    """
+    with open(path, encoding="utf-8") as file:
+        exclusions = yaml.safe_load(file) or {}
+    unknown = set(exclusions) - {"hosts", "prefixes"}
+    if unknown:
+        # a misspelled key would otherwise silently disable those exclusions
+        raise ValueError(f"unknown keys in {path.name}: {sorted(unknown)}")
+    return {key: exclusions.get(key) or {} for key in ("hosts", "prefixes")}
+
+
+def is_excluded_from_prefixcc(
+    prefix: str, namespace: str, exclusions: Mapping[str, Mapping[str, str]]
+) -> bool:
+    """
+    Checks whether a prefix.cc entry is excluded by its prefix or by its namespace's host.
+
+    :param prefix:
+    :param namespace:
+    :param exclusions: as returned by :func:`load_prefixcc_exclusions`
+    :return: True if the entry must not be imported
+    """
+    if prefix in exclusions["prefixes"]:
+        return True
+    try:
+        host = (urlparse(namespace).hostname or "").rstrip(".")
+    except ValueError:
+        # not a URL with a parsable host, such as "http://[abc/"
+        return False
+    return any(
+        host == excluded or host.endswith(f".{excluded}") for excluded in exclusions["hosts"]
+    )
diff --git a/src/prefixmaps/io/parser.py b/src/prefixmaps/io/parser.py
index 347d4bc..e0226ce 100644
--- a/src/prefixmaps/io/parser.py
+++ b/src/prefixmaps/io/parser.py
@@ -54,7 +54,8 @@ def load_context(name: CONTEXT, refresh=False) -> Context:
     Loads a context by name from standard location
 
     :param name:
-    :param refresh: if True, fetch from upstream
+    :param refresh: if True, fetch from upstream. prefix.cc is not curated, so it always
+        comes from the bundled snapshot, see https://github.com/linkml/prefixmaps/issues/61
     :return:
     """
     if refresh:
diff --git a/tests/test_core/test_prefixcc_exclusions.py b/tests/test_core/test_prefixcc_exclusions.py
new file mode 100644
index 0000000..67df56f
--- /dev/null
+++ b/tests/test_core/test_prefixcc_exclusions.py
@@ -0,0 +1,36 @@
+"""Test that no bundled context contains prefix.cc entries that must never be imported."""
+
+import unittest
+
+from prefixmaps import load_context
+from prefixmaps.data import context_paths
+from prefixmaps.ingest.ingest_jsonld import (
+    is_excluded_from_prefixcc,
+    load_prefixcc_exclusions,
+)
+
+
+class TestPrefixCCExclusions(unittest.TestCase):
+    """Test that no bundled context contains prefix.cc entries that must never be imported."""
+
+    def test_no_excluded_entries(self):
+        """Test bundled contexts against prefixcc.excluded.yaml, see issue #61."""
+        exclusions = load_prefixcc_exclusions()
+        hosts_only = {"hosts": exclusions["hosts"], "prefixes": {}}
+        for key in context_paths:
+            with self.subTest(key=key):
+                excluded = [
+                    (expansion.prefix, expansion.namespace)
+                    for expansion in load_context(key).prefix_expansions
+                    # excluded hosts are spam in any source, excluded prefixes only in prefix.cc
+                    if is_excluded_from_prefixcc(
+                        expansion.prefix,
+                        expansion.namespace,
+                        (
+                            exclusions
+                            if "prefixcc" in (key, expansion.expansion_source)
+                            else hosts_only
+                        ),
+                    )
+                ]
+                self.assertEqual([], excluded)
diff --git a/tests/test_etl/test_prefix_cc.py b/tests/test_etl/test_prefix_cc.py
index 8472870..a5c5c23 100644
--- a/tests/test_etl/test_prefix_cc.py
+++ b/tests/test_etl/test_prefix_cc.py
@@ -1,6 +1,19 @@
+import json
+import tempfile
 import unittest
+from pathlib import Path
+from unittest import mock
 
-from prefixmaps.ingest.ingest_jsonld import from_prefixcc
+from prefixmaps.datamodel.context import Context, StatusType
+from prefixmaps.ingest.etl_runner import CONTEXTS, echo_changes, run_etl
+from prefixmaps.ingest.ingest_jsonld import (
+    from_prefixcc,
+    from_prefixcc_snapshot,
+    is_excluded_from_prefixcc,
+    load_prefixcc_exclusions,
+)
+from prefixmaps.io.parser import context_from_file, load_context
+from tests import INPUT_DIR
 
 EXPECTED = [
     ("owl", "http://www.w3.org/2002/07/owl#"),
@@ -18,3 +31,121 @@ def test_prefix_cc(self):
         for pfx, ns in EXPECTED:
             self.assertEqual(pm[pfx], ns)
             self.assertEqual(pmi[ns], pfx)
+
+    def test_prefix_cc_exclusions(self):
+        """Test that excluded entries are dropped when ingesting prefix.cc."""
+        with open(INPUT_DIR / "prefix-cc.context.jsonld", encoding="utf-8") as file:
+            response = mock.Mock(json=mock.Mock(return_value=json.load(file)))
+        with mock.patch("requests.get", return_value=response):
+            pm = from_prefixcc().as_dict()
+        for pfx, ns in EXPECTED:
+            self.assertEqual(pm[pfx], ns)
+        # the input has veelana and ljkl on excluded hosts, and the excluded prefixes leaks and bgcat
+        for pfx in ["veelana", "ljkl", "leaks", "bgcat"]:
+            self.assertNotIn(pfx, pm)
+
+    def test_excluded_hosts(self):
+        """Test that hosts are excluded with their subdomains, but not lookalike domains."""
+        exclusions = {"hosts": {"onlyfans.com": "spam"}, "prefixes": {}}
+        for namespace, expected in [
+            ("https://onlyfans.com/x/", True),
+            ("http://www.onlyfans.com/x/", True),
+            ("https://OnlyFans.com/x/", True),
+            ("https://notonlyfans.com/x/", False),
+            ("https://example.org/onlyfans.com/", False),
+            ("https://onlyfans.com./x/", True),
+            ("http://[abc/", False),
+        ]:
+            with self.subTest(namespace=namespace):
+                self.assertEqual(expected, is_excluded_from_prefixcc("x", namespace, exclusions))
+
+    def test_snapshot(self):
+        """Test that the ETL uses the bundled prefix.cc snapshot without network access."""
+        with mock.patch("requests.get", side_effect=AssertionError("prefix.cc was downloaded")):
+            context = CONTEXTS["prefixcc"]()
+        self.assertEqual(load_context("prefixcc").as_dict(), context.as_dict())
+        self.assertEqual(from_prefixcc_snapshot().as_dict(), context.as_dict())
+        statuses = [pe.canonical() for pe in context.prefix_expansions]
+        self.assertEqual(
+            sorted(statuses, reverse=True), statuses, msg="canonical rows must come first"
+        )
+        # canonical-first ordering only reproduces the merge if prefix.cc has no prefix aliases
+        self.assertNotIn(StatusType.prefix_alias, {pe.status for pe in context.prefix_expansions})
+
+    def test_snapshot_exclusions(self):
+        """Test that a new exclusion is applied to the bundled prefix.cc snapshot."""
+        self.assertIn("foaf", load_context("prefixcc").as_dict())
+        exclusions = {"hosts": {"xmlns.com": "test"}, "prefixes": {}}
+        target = "prefixmaps.ingest.ingest_jsonld.load_prefixcc_exclusions"
+        with mock.patch(target, return_value=exclusions):
+            self.assertNotIn("foaf", from_prefixcc_snapshot().as_dict())
+
+    def test_prefix_cc_without_context(self):
+        """Test that a prefix.cc response without a JSON-LD context is still rejected."""
+        response = mock.Mock(json=mock.Mock(return_value={}))
+        with mock.patch("requests.get", return_value=response):
+            with self.assertRaises(ValueError):
+                from_prefixcc()
+
+    def test_exclusions_loader(self):
+        """Test that empty sections are allowed, but misspelled sections are rejected."""
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / "prefixcc.excluded.yaml"
+            for text, expected in [
+                ("", {"hosts": {}, "prefixes": {}}),
+                ("hosts:\nprefixes:\n  a: spam\n", {"hosts": {}, "prefixes": {"a": "spam"}}),
+            ]:
+                with self.subTest(text=text):
+                    path.write_text(text, encoding="utf-8")
+                    self.assertEqual(expected, load_prefixcc_exclusions(path))
+            path.write_text("prefixess:\n  a: spam\n", encoding="utf-8")
+            with self.assertRaises(ValueError):
+                load_prefixcc_exclusions(path)
+
+    def test_exclusions_file(self):
+        """Test that the exclusions file has reasons for all entries."""
+        exclusions = load_prefixcc_exclusions()
+        for kind, entries in exclusions.items():
+            for entry, reason in entries.items():
+                with self.subTest(kind=kind, entry=entry):
+                    self.assertTrue(reason)
+
+    def test_echo_changes(self):
+        """Test that refreshing prefix.cc reports added and removed expansions."""
+        old, new = Context("prefixcc"), Context("prefixcc")
+        old.add_prefix("a", "https://example.org/a/")
+        old.add_prefix("b", "https://example.org/b/")
+        new.add_prefix("a", "https://example.org/a2/")
+        new.add_prefix("b", "https://example.org/b/")
+        new.add_prefix("c", "https://example.org/c/")
+        new.add_prefix("d", "https://example.org/c/")
+        with mock.patch("click.echo") as echo:
+            echo_changes(old, new)
+        self.assertEqual(
+            [
+                mock.call("- prefixcc a https://example.org/a/ canonical"),
+                mock.call("+ prefixcc a https://example.org/a2/ canonical"),
+                mock.call("+ prefixcc c https://example.org/c/ canonical"),
+                mock.call("+ prefixcc d https://example.org/c/ namespace_alias"),
+            ],
+            echo.call_args_list,
+        )
+
+    def test_refresh_prefixcc(self):
+        """Test that the ETL only downloads prefix.cc when asked, and then reports the changes."""
+        for refresh, expected in [(False, "a"), (True, "b")]:
+            snapshot, download = Context("prefixcc"), Context("prefixcc")
+            snapshot.add_prefix("a", "https://example.org/a/")
+            download.add_prefix("b", "https://example.org/b/")
+            sources = {name: (lambda name=name: Context(name)) for name in CONTEXTS}
+            sources["prefixcc"] = lambda snapshot=snapshot: snapshot
+            target = "prefixmaps.ingest.etl_runner.from_prefixcc"
+            with self.subTest(refresh=refresh), tempfile.TemporaryDirectory() as directory:
+                with mock.patch.dict(CONTEXTS, sources), mock.patch("click.echo") as echo:
+                    with mock.patch(target, return_value=download) as from_prefixcc_mock:
+                        run_etl(directory, refresh_prefixcc=refresh)
+                self.assertEqual(refresh, from_prefixcc_mock.called)
+                self.assertEqual(refresh, echo.called)
+                for name in ["prefixcc", "merged"]:
+                    with open(Path(directory) / f"{name}.csv", encoding="utf-8") as file:
+                        self.assertEqual([expected], list(context_from_file(name, file).as_dict()))