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.

Reviewed October 2026 · 6 min read · By Zenveus Engineering

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How do I fix supabase storage 403 unauthorized or rls upload error?

production-fix-plan.txtrun in order

01# Define the ownership convention

Choose a stable bucket and folder structure tied to user or tenant identity.

02# Add the narrow storage policy

Permit only the authenticated role, bucket, and owned path required by the product.

03# Align the client path

Generate object names that satisfy the policy without trusting arbitrary ownership supplied by users.

04# Test cross-user denial

Verify 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?

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.

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?

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.

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