Embed the snippet

To run experiments, you add one JavaScript snippet to your website. It contains the unique ID of your project. You only install it once: when you change experiments, audiences or settings and publish them, the new data is delivered under the same URL, so the snippet on your site never has to be edited.

<script src="https://cdn.ablyft.com/s/12345678.js"></script>

In this example, 12345678 is the project ID. Replace it with your own.

Get your snippetCopy Anchor Link

1. Open your project in ABlyft.
2. Go to Settings → Snippet.
3. In the section Snippet Implementation, copy the code from Implementation (base snippet).

The same section shows the state of your snippet, see Publishing.

Where to place itCopy Anchor Link

Place the snippet in the <head> of every page you want to test, as early as possible and before your other scripts. A good spot is right after the <title> or the meta tags and stylesheets.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <!-- more meta tags -->
    <!-- stylesheets -->
    <script src="https://cdn.ablyft.com/s/12345678.js"></script>
    <!-- more scripts -->
  </head>
  <body>
    ...
  </body>
</html>

Synchronous or asynchronousCopy Anchor Link

Both variants are supported. Because the snippet loads very quickly, the difference is small. Use the synchronous version if flicker is a concern.

<script async src="https://cdn.ablyft.com/s/12345678.js"></script>

Google Tag ManagerCopy Anchor Link

You can also load the snippet through Google Tag Manager, without changing your site's code.

1. Copy your snippet as described above.
2. In Google Tag Manager, create a new tag of the type Custom HTML.
3. Paste the snippet into the tag.
4. Set the trigger so that the tag fires on the pages you want to test, then publish your container.

Self-hosting the snippetCopy Anchor Link

Instead of the CDN version, you can serve the snippet from your own server. You then save every new version as a file on your side and include that file in your pages. There are two ways to get the current version.

A) Publication webhook (recommended)Copy Anchor Link

ABlyft calls a URL of yours after every publication and sends the snippet in the request. Your script saves it as a local file.

1. In the project, open Settings → Snippet and add the URL of your script under publication webhooks.
2. Add a secret token of your choice as a GET parameter to that URL, for example https://www.example.com/ablyft-webhook.php?token=…, and check it in your script. This prevents others from writing a file with their own content.
3. Include the local file instead of the CDN URL, for example <script src="/snippets/12345678.js"></script>.

<?php
// Example receiver: saves the published snippet as snippets/<project_id>.js
if (($_GET['token'] ?? '') !== 'YOUR_SECRET_TOKEN') {
    http_response_code(403);
    exit;
}

if ($_SERVER['HTTP_USER_AGENT'] !== 'ABlyft Publication Webhook') {
    http_response_code(403);
    exit;
}

$projectId = (int) ($_POST['project_id'] ?? 0);
$script = $_POST['snippet_script'] ?? null;

if ($projectId === 0 || $script === null) {
    http_response_code(400);
    exit;
}

file_put_contents(__DIR__ . "/snippets/{$projectId}.js", $script);
http_response_code(204);

Enable Include JS for the webhook, otherwise the request does not contain snippet_script. The user agent alone is no protection, because anyone can send it; the token is what secures the endpoint.

B) Pull the file from the CDNCopy Anchor Link

Your server can also download the snippet from its CDN address on a schedule or on demand. In this case the cache expiration (ttl) must be set to Disable Caching, so that you always receive the latest version. This setting is read-only in the app, so ask ABlyft support to change it. See Cache expiration.

Good to knowCopy Anchor Link

• Include it once per page. If a second ABlyft snippet is found, it logs a warning and does not start.
• iFrames: The snippet does not run inside iFrames by default, see Requirements.
• Environments: to load less data on a specific site, use a sub-snippet instead of the main snippet.
• Bots are excluded, see Requirements.
• Consent: If you need visitor consent before tracking, see Consent manager.
• Updates: After publishing in ABlyft, it can take a short time until the new version is delivered, see Cache expiration.

Check the installationCopy Anchor Link

Verify that the snippet is requested and running with the checks in Verify the integration, or follow the Quickstart.