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You're halfway down a page, an ad or a batch of new posts loads above you, and the paragraph you were reading slides off the screen. Since Safari 27, every major browser fights that jump for you. Scroll anchoring, and the overflow-anchor property that controls it, became Baseline on September 14, 2026.

What surprised me is how old this is: MDN's compatibility data lists Chrome 56 and Firefox 66. What was missing was Safari, and with it the iPhone.

What scroll anchoring does

The classic behaviour of a scroll container is to keep its scroll offset fixed. If something 300 px tall appears above what you're looking at, the offset stays the same, so everything you can see moves down by 300 px. The spec's introduction names the usual culprits: script inserting an ad iframe, or images without dimensions loading on a slow network.

Scroll anchoring flips that.…