Google has introduced side rail ads, a new AdSense ad format. Side rails are ads that stick to the sides of your pages when viewed on widescreen devices such as desktops.
Google wrote:
“Today, we’re announcing a new ad format called side rails. Side rails are ads that stick to the sides of your pages when they’re viewed on widescreen devices, such as desktops.”
Google also added that websites owners who already have anchor ads enabled, side rails will automatically start to appear on their websites after December 13, 2022.
“If you already have anchor ads turned on, side rails will automatically start to appear on your site after December 13, 2022,” according to Google.
If you don’t want to see side rails, you can disable this option in your Auto ads settings within your AdSense console.