Custom Loader power-up

The Custom Loader power-up minimizes the impact of ad blockers on your GTM and GA4 scripts by routing them through a path that turns all cookies into first-party cookies.

Custom Loader is available on the Free subscription plan and higher. To check your current plan or upgrade, go to your sGTM container settings.

1. Log in to your Stape account and select your sGTM container from the dashboard.

2. Go to Power-ups and click Use next to the Custom Loader panel.

3. Toggle the Custom Loader switch to enable it.

4. If you want to encode tracking requests sent from the browser to your sGTM container, toggle the Enhanced ad blocker protection. By masking recognizable URL patterns and tracking signatures, it prevents ad blockers from identifying and intercepting those requests.

5. Click Save changes.

6. In the Code & Setup information section, choose the Platform - here you can either:

• Select your CMS platform (such as Shopify, Wordpress, etc.). In this case, you’ll be required to install and configure a Stape app. 
• Select Other to receive a JS snippet in case you’re using another platform or a custom website.

To verify the setup is working:

1. 1.
   Open any page on your website.
2. 2.
   Right-click → Inspect → open the Network tab.
3. 3.
   Filter requests by your custom subdomain or same-origin path.
4. 4.
   Look for the GTM request URL - it should return a 200 OK status code.

GTM Environments let you load a specific version of your container (e.g., staging or development) instead of the published version. If you use environments, you need to manually add the environment parameters to your Custom Loader code.

1. Get your environment parameters.

• In web GTM, go to Admin → Environments.

• Find your environment and click Actions → Get Snippet.

• Copy the three parameters from the snippet URL: gtm_auth, gtm_preview, and gtm_cookies_win.

2. Add the environment parameters to the head snippet.

In the generated Custom Loader head code, locate the E.src line. 

Append the parameters to the query string: 

Be sure to replace gtm_auth, gtm_preview, and gtm_cookies_win in the example with your own respective parameters. Also, it is highly recommended to add new parameters at the end of the URL string to avoid breaking anything (i.e., do NOT add them in the middle like E.src=f+"/"+i+".js?"+c+new parameters+v).

3. Add the environment parameters to the body snippet.

Do the same for the body snippet:

Append the same parameters to the iframe URL in the body snippet (replace the gtm_auth, gtm_preview, and gtm_cookies_win in the example with your own respective parameters):

A sample scenario is an eCommerce store that sees significant data loss because a large share of its users have ad blockers installed. By enabling Custom Loader, all GTM and GA4 scripts load from a first-party domain, so ad blockers no longer recognize and block them.

You can spot the data loss this way:

1. 1.
   Compare the order count in your backend against Purchase events in GA4 for the same period. If your backend shows 500 purchases but GA4 only reports 380, the gap could be caused by ad blockers preventing the GTM script from loading in users' browsers entirely. 
2. 2.
   Enable Custom Loader. This reroutes GTM and GA4 scripts through your first-party domain, so ad blockers can no longer identify and block them by URL pattern.
3. 3.
   Monitor your GA4 Purchase event count over the same time window and compare it against your backend again.

If the gap persists after enabling Custom Loader, turn on the Enhanced ad blocker protection as well. This encrypts the request URLs so that blocking rules can't match them.