---
description: Allow or deny a request based on a known pre-shared key in a header. This is not meant to replace the [WebCrypto API](/workers/runtime-apis/web-crypto/).
title: Auth with headers
image: https://developers.cloudflare.com/og-docs.png
---

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# Auth with headers

Allow or deny a request based on a known pre-shared key in a header. This is not meant to replace the [WebCrypto API](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/workers/runtime-apis/web-crypto/).

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/rules/snippets/examples/auth-with-headers/index.md)|[Agent setup](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/agent-setup/)

Caution when using in production

The example code contains a generic header key and value of `X-Custom-PSK` and `mypresharedkey`. To best protect your resources, change the header key and value in the Snippets editor before saving your code.

```js
export default {
	async fetch(request) {
		/**
		 * @param {string} PRESHARED_AUTH_HEADER_KEY Custom header to check for key
		 * @param {string} PRESHARED_AUTH_HEADER_VALUE Hard-coded key value
		 */
		const PRESHARED_AUTH_HEADER_KEY = "X-Custom-PSK";
		const PRESHARED_AUTH_HEADER_VALUE = "mypresharedkey";
		const psk = request.headers.get(PRESHARED_AUTH_HEADER_KEY);

		if (psk === PRESHARED_AUTH_HEADER_VALUE) {
			// Correct preshared header key supplied. Fetch request from origin.
			return fetch(request);
		}

		// Incorrect key supplied. Reject the request.
		return new Response("Sorry, you have supplied an invalid key.", {
			status: 403,
		});
	},
};
```

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```