---
title: Validate JWTs · Cloudflare Zero Trust docs
description: When Cloudflare sends a request to your origin, the request will
  include an application token as a Cf-Access-Jwt-Assertion request header.
  Requests made through a browser will also pass the token as a CF_Authorization
  cookie.
lastUpdated: 2025-10-10T18:46:14.000Z
chatbotDeprioritize: false
source_url:
  html: https://developers.cloudflare.com/cloudflare-one/identity/authorization-cookie/validating-json/
  md: https://developers.cloudflare.com/cloudflare-one/identity/authorization-cookie/validating-json/index.md
---

When Cloudflare sends a request to your origin, the request will include an [application token](https://developers.cloudflare.com/cloudflare-one/identity/authorization-cookie/application-token/) as a `Cf-Access-Jwt-Assertion` request header. Requests made through a browser will also pass the token as a `CF_Authorization` cookie.

Cloudflare signs the token with a key pair unique to your account. You should validate the token with your public key to ensure that the request came from Access and not a malicious third party. We recommend validating the `Cf-Access-Jwt-Assertion` header instead of the `CF_Authorization` cookie, since the cookie is not guaranteed to be passed.

## Access signing keys

The public key for the signing key pair is located at `https://<your-team-name>.cloudflareaccess.com/cdn-cgi/access/certs`, where `<your-team-name>` is your Zero Trust team name.

By default, Access rotates the signing key every 6 weeks. This means you will need to programmatically or manually update your keys as they rotate. Previous keys remain valid for 7 days after rotation to allow time for you to make the update.

You can also manually rotate the key using the [API](https://developers.cloudflare.com/api/resources/zero_trust/subresources/access/subresources/keys/methods/rotate/). This can be done for testing or security purposes.

As shown in the example below, `https://<your-team-name>.cloudflareaccess.com/cdn-cgi/access/certs` contains two public keys: the current key used to sign all new tokens, and the previous key that has been rotated out.

* `keys`: both keys in JWK format
* `public_cert`: current key in PEM format
* `public_certs`: both keys in PEM format

```txt
{
  "keys": [
    {
      "kid": "1a1c3986a44ce6390be42ec772b031df8f433fdc71716db821dc0c39af3bce49",
      "kty": "RSA",
      "alg": "RS256",
      "use": "sig",
      "e": "AQAB",
      "n": "5PKw-...-AG7MyQ"
    },
    {
      "kid": "6c3bffef71bb0a90c9cbef3b7c0d4a1c7b4b8b76b80292a623afd9dac45d1c65",
      "kty": "RSA",
      "alg": "RS256",
      "use": "sig",
      "e": "AQAB",
      "n": "pwVn...AA6Hw"
    }
  ],
  "public_cert": {
    "kid": "6c3bffef71bb0a90c9cbef3b7c0d4a1c7b4b8b76b80292a623afd9dac45d1c65",
    "cert": "-----BEGIN CERTIFICATE----- ... -----END CERTIFICATE----- "
  },
  "public_certs": [
    {
      "kid": "1a1c3986a44ce6390be42ec772b031df8f433fdc71716db821dc0c39af3bce49",
      "cert": "-----BEGIN CERTIFICATE----- ... -----END CERTIFICATE----- "
    },
    {
      "kid": "6c3bffef71bb0a90c9cbef3b7c0d4a1c7b4b8b76b80292a623afd9dac45d1c65",
      "cert": "-----BEGIN CERTIFICATE----- ... -----END CERTIFICATE----- "
    }
  ]
}
```

Avoid key rotation issues

* Validate tokens using the external endpoint rather than saving the public key as a hard-coded value.
* Do not fetch the current key from `public_cert`, since your origin may inadvertently read an expired value from an outdated cache. Instead, match the `kid` value in the JWT to the corresponding certificate in `public_certs`.

## Verify the JWT manually

To verify the token manually:

1. Copy the JWT from the `Cf-Access-Jwt-Assertion` request header.

2. Go to [jwt.io](https://jwt.io/).

3. Select the RS256 algorithm.

4. Paste the JWT into the **Encoded** box.

5. In the **Payload** box, ensure that the `iss` field points to your team domain (`https://<your-team-name>.cloudflareaccess.com`). `jwt.io` uses the `iss` value to fetch the public key for token validation.

6. Ensure that the page says **Signature Verified**.

You can now trust that this request was sent by Access.

## Programmatic verification

You can run an automated script on your origin server to validate incoming requests. The provided sample code gets the application token from a request and checks its signature against your public key. You will need to insert your own team domain and Application Audience (AUD) tag into the sample code.

### Get your AUD tag

Cloudflare Access assigns a unique AUD tag to each application. The `aud` claim in the token payload specifies which application the JWT is valid for.

To get the AUD tag:

1. In [Zero Trust](https://one.dash.cloudflare.com/), go to **Access** > **Applications**.
2. Select **Configure** for your application.
3. From the **Basic information** tab, copy the **Application Audience (AUD) Tag**.

You can now paste the AUD tag into your token validation script. The AUD tag will never change unless you delete or recreate the Access application.

### Cloudflare Workers example

When Cloudflare Access is in front of your [Worker](https://developers.cloudflare.com/workers), your Worker still needs to validate the JWT that Cloudflare Access adds to the `Cf-Access-Jwt-Assertion` header on the incoming request.

The following code will validate the JWT using the [jose NPM package](https://www.npmjs.com/package/jose):

```javascript
import { jwtVerify, createRemoteJWKSet } from 'jose';


export default {
  async fetch(request, env, ctx) {
    // Verify the POLICY_AUD environment variable is set
    if (!env.POLICY_AUD) {
      return new Response('Missing required audience', {
        status: 403,
        headers: { 'Content-Type': 'text/plain' }
      });
    }


    // Get the JWT from the request headers
    const token = request.headers.get('cf-access-jwt-assertion');


    // Check if token exists
    if (!token) {
      return new Response('Missing required CF Access JWT', {
        status: 403,
        headers: { 'Content-Type': 'text/plain' }
      });
    }


    try {
      // Create JWKS from your team domain
      const JWKS = createRemoteJWKSet(new URL(`${env.TEAM_DOMAIN}/cdn-cgi/access/certs`));


      // Verify the JWT
      const { payload } = await jwtVerify(token, JWKS, {
        issuer: env.TEAM_DOMAIN,
        audience: env.POLICY_AUD,
      });


      // Token is valid, proceed with your application logic
      return new Response(`Hello ${payload.email || 'authenticated user'}!`, {
        headers: { 'Content-Type': 'text/plain' }
      });


    } catch (error) {
      // Token verification failed
      return new Response(`Invalid token: ${error.message}`, {
        status: 403,
        headers: { 'Content-Type': 'text/plain' }
      });
    }
  },
};
```

#### Required environment variables

Add these [environment variables](https://developers.cloudflare.com/workers/configuration/environment-variables/) to your Worker:

* `POLICY_AUD`: Your application's [AUD tag](#get-your-aud-tag)
* `TEAM_DOMAIN`: `https://<your-team-name>.cloudflareaccess.com`, where `<your-team-name>` is replaced with your actual team name.

You can set these variables by adding them to your Worker's [Wrangler configuration file](https://developers.cloudflare.com/workers/wrangler/configuration/), or via the Cloudflare dashboard under **Workers & Pages** > **your-worker** > **Settings** > **Environment Variables**.

### Golang example

```go
package main


import (
    "context"
    "fmt"
    "net/http"


    "github.com/coreos/go-oidc/v3/oidc"
)


var (
    ctx        = context.TODO()
    teamDomain = "https://test.cloudflareaccess.com"
    certsURL   = fmt.Sprintf("%s/cdn-cgi/access/certs", teamDomain)


    // The Application Audience (AUD) tag for your application
    policyAUD = "4714c1358e65fe4b408ad6d432a5f878f08194bdb4752441fd56faefa9b2b6f2"


    config = &oidc.Config{
        ClientID: policyAUD,
    }
    keySet   = oidc.NewRemoteKeySet(ctx, certsURL)
    verifier = oidc.NewVerifier(teamDomain, keySet, config)
)


// VerifyToken is a middleware to verify a CF Access token
func VerifyToken(next http.Handler) http.Handler {
    fn := func(w http.ResponseWriter, r *http.Request) {
        headers := r.Header


        // Make sure that the incoming request has our token header
        //  Could also look in the cookies for CF_AUTHORIZATION
        accessJWT := headers.Get("Cf-Access-Jwt-Assertion")
        if accessJWT == "" {
            w.WriteHeader(http.StatusUnauthorized)
            w.Write([]byte("No token on the request"))
            return
        }


        // Verify the access token
        ctx := r.Context()
        _, err := verifier.Verify(ctx, accessJWT)
        if err != nil {
            w.WriteHeader(http.StatusUnauthorized)
            w.Write([]byte(fmt.Sprintf("Invalid token: %s", err.Error())))
            return
        }
        next.ServeHTTP(w, r)
    }
    return http.HandlerFunc(fn)
}


func MainHandler() http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("welcome"))
    })
}


func main() {
    http.Handle("/", VerifyToken(MainHandler()))
    http.ListenAndServe(":3000", nil)
}
```

### Python example

`pip` install the following:

* flask
* requests
* PyJWT
* cryptography

```python
from flask import Flask, request
import requests
import jwt
import json
import os
app = Flask(__name__)




# The Application Audience (AUD) tag for your application
POLICY_AUD = os.getenv("POLICY_AUD")


# Your CF Access team domain
TEAM_DOMAIN = os.getenv("TEAM_DOMAIN")
CERTS_URL = "{}/cdn-cgi/access/certs".format(TEAM_DOMAIN)


def _get_public_keys():
    """
    Returns:
        List of RSA public keys usable by PyJWT.
    """
    r = requests.get(CERTS_URL)
    public_keys = []
    jwk_set = r.json()
    for key_dict in jwk_set['keys']:
        public_key = jwt.algorithms.RSAAlgorithm.from_jwk(json.dumps(key_dict))
        public_keys.append(public_key)
    return public_keys


def verify_token(f):
    """
    Decorator that wraps a Flask API call to verify the CF Access JWT
    """
    def wrapper():
        # Check for the POLICY_AUD environment variable
        if not POLICY_AUD:
          return "missing required audience", 403


        token = ''
        if 'CF_Authorization' in request.cookies:
            token = request.cookies['CF_Authorization']
        else:
            return "missing required cf authorization token", 403
        keys = _get_public_keys()


        # Loop through the keys since we can't pass the key set to the decoder
        valid_token = False
        for key in keys:
            try:
                # decode returns the claims that has the email when needed
                jwt.decode(token, key=key, audience=POLICY_AUD, algorithms=['RS256'])
                valid_token = True
                break
            except:
                pass
        if not valid_token:
            return "invalid token", 403


        return f()
    return wrapper




@app.route('/')
@verify_token
def hello_world():
    return 'Hello, World!'




if __name__ == '__main__':
    app.run()
```

### JavaScript (Node.js) example

```javascript
const express = require("express");
const jose = require("jose");


// The Application Audience (AUD) tag for your application
const AUD = process.env.POLICY_AUD;


// Your CF Access team domain
const TEAM_DOMAIN = process.env.TEAM_DOMAIN;
const CERTS_URL = `${TEAM_DOMAIN}/cdn-cgi/access/certs`;


const JWKS = jose.createRemoteJWKSet(new URL(CERTS_URL));


// verifyToken is a middleware to verify a CF authorization token
const verifyToken = async (req, res, next) => {
  // Check for the AUD environment variable
  if (!AUD) {
    return res.status(403).send({
      status: false,
      message: "missing required audience",
    });
  }


  const token = req.headers["cf-access-jwt-assertion"];


  // Make sure that the incoming request has our token header
  if (!token) {
    return res.status(403).send({
      status: false,
      message: "missing required cf authorization token",
    });
  }


  try {
    const result = await jose.jwtVerify(token, JWKS, {
      issuer: TEAM_DOMAIN,
      audience: AUD,
    });


    req.user = result.payload;
    next();
  } catch (err) {
    return res.status(403).send({
      status: false,
      message: "invalid token",
    });
  }
};


const app = express();


app.use(verifyToken);


app.get("/", (req, res) => {
  res.send("Hello World!");
});


app.listen(3333);
```
