Playbook: Kill CLS from your mobile anchor

Playbook: Kill CLS from your mobile anchor
What it does: the bottom anchor is a stealth CLS source — this stops it shifting content.

Setup (effort 1/5):
— Reserve the anchor height with a fixed padding-bottom on body equal to the anchor (usually 50-100px).
— Position the anchor fixed, so it overlays rather than pushes layout.
— Never animate the anchor sliding in on load — that animation IS the layout shift CrUX records.
— Test in PageSpeed field data; lab tools often miss anchor-driven shift.
— Confirm the close button doesn't reflow content when tapped — collapse to reserved space, not zero.

RPM lift seen: indirect — protects the anchor's strong RPM by keeping CWV green.

Pros: ten-minute fix, real CWV gain. Cons: a fixed bottom bar eats a sliver of viewport.

Lift: ★★★☆☆ — Risk: ★☆☆☆☆
Best for: anyone running a mobile anchor (most do). Skip if you don't.