Using Google Publisher Tags (GPT tags)? Don't forget to update the hosted library domain

Here's a handy tip for anyone using Google Publisher Tags (GPT tags) to serve ads with Google Ad Manager. It's a small change you can make to speed up your tags (and hence your ad fetching).

So... over the past couple of years I've added Google Publisher Tags to a number of websites, including this one. When generating a tag for a new site today, I noticed that it was subtly different to the version I had used previously.

Here's how the code for the document <head> used to begin:


Compare this to the tag that Google Ad Manager generates now:


As well as being more concise, the obvious big difference is that the Google Publisher Tag library (gpt.js) is now hosted in a different location.

Google Ad Manager Help has an explanation:

The Google Publisher Tag library is now hosted at, in addition to being hosted at the domain. While not required, we strongly recommend that you update all references to GPT on your pages to use this new domain.

This change consolidates all ad serving requests to one domain, instead of two, which means the browser only needs to connect to one domain. The library is exactly the same at both domains.

The result is an improvement in the speed of your tags and fetching ads a bit quicker.

That "in addition to" is important. The library will continue to be hosted at its old location (as well as the new one), so nobody's ads will suddenly stop serving. That's probably why the change has gone unnoticed (by me at least).

It didn't pass everyone by, though - the ever-vigilant Drupal community picked up on it back in June 2019. However as I only happened to spot it by accident four months later, perhaps Google could have done more to make publishers aware. A prominent notification in Google Ad Manager itself would be my suggestion.

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James Clark
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