01Confirm the upload is authenticated
Inspect the active user and token at the moment the upload runs.
What the result tells you: An anonymous request will not satisfy a policy written for authenticated users.
ERR-747/Supabase Storage · 403 / RLS upload error
Appears when: 403 / RLS upload error
Supabase Storage 403 unauthorized or RLS upload error
The upload request reached Storage, but the authenticated role is not allowed to create the corresponding object row. Check the session, bucket and object path, and storage.objects policies; keep the bucket policy narrow instead of bypassing authorization.
How do I fix supabase storage 403 unauthorized or rls upload error?
01
# Define the ownership conventionChoose a stable bucket and folder structure tied to user or tenant identity.02
# Add the narrow storage policyPermit only the authenticated role, bucket, and owned path required by the product.03
# Align the client pathGenerate object names that satisfy the policy without trusting arbitrary ownership supplied by users.04
# Test cross-user denialVerify the owner can upload and another user cannot overwrite or read private content.Preserve the current working revision, change one proven boundary, and verify the published path in a clean session.
What if the quick fix does not work?
02Inspect the complete object path
Record bucket id, folder segments, and filename exactly as the client sends them.
What the result tells you: A policy that expects the user id in the first folder fails when the path uses another shape.
03Read storage.objects policies
Check INSERT for uploads and SELECT for later retrieval. Upsert may require additional permissions.
What the result tells you: A public bucket controls reading, not unrestricted client uploads.
| Likely cause | What proves it | First safe action |
|---|---|---|
| Missing storage INSERT policy | An anonymous request will not satisfy a policy written for authenticated users. | Define the ownership convention |
| Path does not match the policy | A policy that expects the user id in the first folder fails when the path uses another shape. | Add the narrow storage policy |
| Expired or absent session | A public bucket controls reading, not unrestricted client uploads. | Align the client path |
| Upsert needs more permission | An anonymous request will not satisfy a policy written for authenticated users. | Test cross-user denial |
Why do AI-built apps hit this problem?
The upload request reached Storage, but the authenticated role is not allowed to create the corresponding object row. Check the session, bucket and object path, and storage.objects policies; keep the bucket policy narrow instead of bypassing authorization.
Missing storage INSERT policy
The bucket exists, but authenticated users have no rule for creating object rows.
Path does not match the policy
The folder ownership convention and actual object name disagree.
Expired or absent session
The client uploads before the auth state is ready.
When the built-in AI fix makes it worse
Freeze generated changes, restore the last known working version, reproduce one request, collect the browser and platform logs, and change one layer at a time.
How do I stop this problem recurring?
- →Document the bucket, path, ownership, read, write, and delete rules together.
- →Test upload, read, replacement, and deletion as separate operations.
- →Keep production configuration in an explicit release checklist, not in chat history.
- →Test the published URL in a clean browser session before calling the release complete.
- →Keep a last-known-good deployment and a documented rollback step.
- →Log the critical request path with enough context to identify the failing layer.
Still stuck with supabase storage 403 unauthorized or rls upload error?
AI prototype hardeningWe restore the critical path and document the root cause.
- Production failure reproduced with evidence
- The smallest responsible layer repaired
- Rollback and prevention guidance included
Supabase Storage 403 unauthorized or RLS upload error questions
Does a public bucket allow public uploads?+
No. Public bucket behavior primarily affects retrieval. Upload authorization still depends on storage policies.
Why can the service role upload?+
The service role is privileged and server-only. Its success does not validate a browser user policy.
Should I expose the service key in the frontend?+
Never. Keep it server-side and repair the authenticated storage policy.
Take it further
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