workerd error: request body too large

workerd error: request body too large

TL;DR

The request body exceeds workerd's limit. Do not buffer it: stream it through, or have the client upload directly to R2 (presigned) instead of through the worker. Workers are not file servers.

workerd error: request body too large

Steps

1. Check the body size against the limit. Expected: The overage is confirmed.

2. Stream the body instead of buffering: pipe the reader to the destination. Expected: Memory stays flat and limits are respected.

3. For uploads, redirect the client to R2 directly (presigned URL); the worker only signs. Expected: The worker never sees the bytes.

4. If the body must pass through, chunk it. Expected: No single request carries the whole thing.

5. Enforce a client-side size check before upload for a clean error. Expected: Users get a clear message, not a workerd error.

When to use

• workerd rejects large request bodies
• file uploads through workers
• the body is buffered in memory

When not to use

• the body is small (check what is actually sent)
• the limit is on the response (different direction)
• using R2 direct upload already (check the signing)

Tool compatibility

• workerd
• Cloudflare Workers

Variant phrasings

• "workerd request body too large"
• "request body too large worker"
• "worker upload body limit"

Why it happens

Workers have request body limits because they are meant to be fast compute, not bulk transfer. Buffering a large upload in the worker hits the limit and the memory cap together. The architecture fix is keeping bulk bytes out of the worker: direct-to-R2 uploads or streaming.

Edge cases

• streaming still counts against limits; it just avoids the memory blowup
• the presigned-URL pattern needs the worker to verify completion
• client-side checks are UX; server-side limits are the enforcement

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_8q3fWTGJ9eqcXEwvgXC84Q