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Serve private images using signed URL tokens

If an image is marked to require a signed URL, it cannot be accessed without a token unless it is being requested for a Variant that is set to always allow public access.

  1. Log in to the Cloudflare dashboard, and select your account.
  2. Click Images > Keys.
  3. Copy your key and use it to generate an expiring tokenized URL. Here is an example Worker script that takes in a regular URL without a signed token and returns a tokenized URL that expires after one day. You can, however, set this expiration period to whatever you need, by changing the const EXPIRATION value.
    const EXPIRATION = 60 * 60 * 24; // 1 day
    const bufferToHex = buffer =>
    [ Uint8Array(buffer)].map(x => x.toString(16).padStart(2, '0')).join('');
    async function generateSignedUrl(url) {
    // `url` is a full URL
    // e.g.
    const encoder = new TextEncoder();
    const secretKeyData = encoder.encode(KEY);
    const key = await crypto.subtle.importKey(
    { name: 'HMAC', hash: 'SHA-256' },
    // Attach the expiration value to the `url`
    const expiry = Math.floor( / 1000) + EXPIRATION;
    url.searchParams.set('exp', expiry);
    // `url` now looks like
    const stringToSign = url.pathname + '?' + url.searchParams.toString();
    // for example, /cheeW4oKsx5ljh8e8BoL2A/bc27a117-9509-446b-8c69-c81bfeac0a01/mobile?exp=1631289275
    // Generate the signature
    const mac = await crypto.subtle.sign('HMAC', key, encoder.encode(stringToSign));
    const sig = bufferToHex(new Uint8Array(mac).buffer);
    // And attach it to the `url`
    url.searchParams.set('sig', sig);
    return new Response(url);
    addEventListener('fetch', event => {
    const url = new URL(event.request.url);
    const imageDeliveryURL = new URL(
    url.pathname.slice(1).replace('https:/', '')