The source – support.google.com
The Google AdSense team announced upcoming support for fixed ads on more screens of various sizes. They will start appearing on wide screens from July 19, 2021. It is important that users can close them at any time.
If such ads are enabled on the site, they will soon start showing on desktops. Service experiments show that this is effective. However, you can also turn off the Widescreen feature in your Auto Ads settings.
To analyze the performance of your site's fixed ads, you must enable them to appear after configuring your automated ads.