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Error library

Cloudflare Error 1101: Rendering error (Worker exception)

Cloudflare shows Error 1101 when a Worker (including Pages Functions) hits a runtime JavaScript exception. Check the Worker logs for the exception and fix it in code.

Cause: Uncaught runtime exception in Worker code.

How to fix it

  1. Open Workers & Pages > your project > Logs, or tail logs with Wrangler.
  2. Look for undefined variables, type errors, rejected promises, or failed fetches.
  3. Check bindings and env vars exist in the deployed environment.
  4. Reproduce locally with wrangler dev.

Example

Illustrative example, not from a customer project.

- const data = await env.DB.prepare(sql).all()
+ if (!env.DB) return new Response('DB binding missing', { status: 500 })
+ const data = await env.DB.prepare(sql).all()

FAQ

Is my site down for everyone?

For requests hitting that code path, yes, until the exception is fixed.

What should I send Cloudflare support?

Their docs ask for the Ray ID, Worker name, recent changes and repro steps.

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