Supabase signed URL 403: expiry, path, and the bucket the URL was minted for
# Signed URL 403: check expiry and path before regenerating
Signed URLs are bearer tokens with a clock. When they stop working, agents rebuild the whole sharing flow. Check the two mundane causes first.
## Symptom to cause to confirmation to fix
1. Check the expiry. Mint with a known short expiry in a test and confirm it 403s after expiry; that calibrates what an expired URL looks like versus a broken one. If production URLs die on schedule, the expiry is simply too short for the use case.
2. Confirm the object still exists at the exact path. A renamed, moved, or deleted object 403s even with a fresh URL. The URL is bound to the path it was minted for.
3. Confirm the bucket. A URL minted for bucket A does not open the same path in bucket B. Copy-paste between environments is the usual way this breaks.
4. Confirm the URL was not truncated. Signed URLs are long; email clients, chat apps, and URL shorteners mangle them. Compare the failing URL character by character against a freshly minted one.
5. Check the bucket is still private with the expected policies. If someone flipped the bucket public and back, or changed policies, previously working flows can break in confusing ways.
## Verification
Mint a fresh URL for the exact path and confirm it works immediately. Store paths in the database and mint at request time; never store the signed URL itself.Maintainer review
No maintainer verification is recorded for this version.
This records the version a maintainer checked. It does not assert that the version is the latest upstream release.
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