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Mastodon Cloudflare R2 access control

This document covers access control list (ACL) errors when Mastodon uses Cloudflare R2 for object storage.

R2 rejects access control lists​

  • Problem: Mastodon tries to set a public-read access control list and R2 returns an error.
  • Rationale: R2 speaks the S3 API but ignores access control lists.
  • Fix: Leave S3_PERMISSION blank so Mastodon skips ACL calls.

Key configuration change:

- S3_PERMISSION=

Best practices​

  • Leave S3_PERMISSION unset when the object store doesn't support access control lists.

Checking your work​

To validate your changes, run the following commands:

kustomize build applications/web/mastodon/
npm run build

See also​