diff --git a/src/web/static/js/app.js b/src/web/static/js/app.js
index c0487d95..82d77fc1 100644
--- a/src/web/static/js/app.js
+++ b/src/web/static/js/app.js
@@ -1256,15 +1256,28 @@ function encodeUploadMetadata(metadata) {
 /**
  * 生成 Idempotency-Key (epoch_ms-UUID)
  */
+function uuidFromRandomValues(cryptoObj) {
+    if (!cryptoObj || typeof cryptoObj.getRandomValues !== 'function') {
+        throw new Error('no Web Crypto random source available in this environment');
+    }
+    const bytes = cryptoObj.getRandomValues(new Uint8Array(16));
+    bytes[6] = (bytes[6] & 0x0f) | 0x40;
+    bytes[8] = (bytes[8] & 0x3f) | 0x80;
+    const hex = Array.from(bytes, (byte) => byte.toString(16).padStart(2, '0')).join('');
+    return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
+}
+
 function generateUploadIdempotencyKey() {
     const epoch = Date.now();
     const cryptoObj = typeof crypto !== 'undefined'
         ? crypto
         : (typeof globalThis !== 'undefined' && globalThis.crypto ? globalThis.crypto : null);
-    if (!cryptoObj || typeof cryptoObj.randomUUID !== 'function') {
-        throw new Error('crypto.randomUUID is not supported in this environment');
+    let uuid = null;
+    if (cryptoObj && typeof cryptoObj.randomUUID === 'function') {
+        uuid = cryptoObj.randomUUID();
+    } else {
+        uuid = uuidFromRandomValues(cryptoObj);
     }
-    const uuid = cryptoObj.randomUUID();
     return `${epoch}-${uuid}`;
 }
 
diff --git a/src/web/tests/local-upload.test.js b/src/web/tests/local-upload.test.js
index c9af460c..b57e2630 100644
--- a/src/web/tests/local-upload.test.js
+++ b/src/web/tests/local-upload.test.js
@@ -152,6 +152,23 @@ describe('local upload frontend logic', () => {
     expect(key).toMatch(/^\d+-[0-9a-fA-F-]+$/);
   });
 
+  it('still generates epoch_ms-UUID keys when crypto.randomUUID is unavailable (plain HTTP origin)', async () => {
+    await installIndexPage();
+    const { window } = dom;
+
+    const originalCrypto = window.crypto;
+    Object.defineProperty(window, 'crypto', {
+      configurable: true,
+      value: { getRandomValues: (array) => originalCrypto.getRandomValues(array) },
+    });
+    try {
+      const key = window.generateUploadIdempotencyKey();
+      expect(key).toMatch(/^\d+-[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/);
+    } finally {
+      Object.defineProperty(window, 'crypto', { configurable: true, value: originalCrypto });
+    }
+  });
+
   it('switches between URL mode and Upload mode without breaking URL transcription', async () => {
     await installIndexPage();
     const { document } = dom.window;