---
description: Troubleshoot HTTP 501 error responses.
title: Error 501
image: https://developers.cloudflare.com/og-docs.png
---

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# Error 501

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-501/index.md)|[Agent setup](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/agent-setup/)

## Error 501: not implemented

Cloudflare Workers returns a `501` error when a request uses an HTTP method that is not supported by the Workers Runtime.

### Common causes

* A client sent a request to a Workers script using a custom or non-standard HTTP method (methods outside of `GET`, `POST`, `PUT`, etc.).
* A typo in the HTTP method (for example, `POT` instead of `POST`).

### Resolution

* Update the client to use a valid, standard [HTTP request method ↗](https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods).

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