Did you see this error in the Chrome developer tools?

The resource https://pagead2.googlesyndication.com/pagead/js/r20190624/r20190131/show_ads_impl.js was preloaded using link preload but not used within a few seconds from the window’s load event. Please make sure it has an appropriate ‘as’ value and it is preloaded intentionally.

You would not be the first one and after a few questions from Advanced Ads users, I thought I might dig into the meaning of it.

When does this warning show up?

The warning only shows in the developer tools in the Chrome browser for websites that are using AdSense. It doesn’t matter whether you are using their Auto ads feature or manually placed AdSense ads.

Does it hurt your AdSense earnings?

While I am still waiting for confirmation from AdSense, I am very sure that this doesn’t hurt your AdSense earnings. The technical details aside, if this warning would have a consequence like a reduced earning potential then it would not show on all websites using AdSense and not be fixed quickly by Google.

The problem could be a small one related to performance. If a file is loaded and then not used, it might be better to not load it at all. My tests show that this is maybe in the range of 250 ms and file size of 78.5 kB.

What are the technical details?

If you take a look at any AdSense code then you see them loading a JavaScript with the following code.

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>

This is obviously not the script show_ads_impl.js mentioned in the warning above. However, this file loads that script which is using the preload technique. It basically means that AdSense intends to use (parts of) that file and asks the browser to load it for later.

The warning shows up because the file is then not used within 3 seconds after requesting it, or technically, after the onload event fired.

Preloading was introduced in Chrome 50. The preload value will just be ignored by browsers not supporting it and does not cause any issues. The standard might still change in the future.

How can you solve this?

It is not on you to solve this issue. Since the file is referenced in the AdSense code, only they can rewrite it to not load the script if not needed or to use a technique that doesn’t provoke a warning.

I am waiting on an official response from AdSense about this and will update this post if I receive it. If you want to add some more details here then please reach out directly.