Playbook: Audit CLS your ads are causing

Playbook: Audit CLS your ads are causing
What it does: finds which ad slots tank Core Web Vitals — and the revenue trade.

Setup (effort 3/5):
— Open Chrome DevTools > Performance > record a load. Filter Layout Shift entries; each names the shifting node.
— Cross-reference shift sources against ad container IDs. The repeat offenders are your unreserved slots.
— Fix: set explicit min-height per slot matching its most common creative size (e.g. 280px for a 300x250).
— Re-measure CLS in PageSpeed field data (CrUX), not lab — lab misses real fill timing.
— Hold a slot's height even on no-fill. Collapsing empty slots is a top hidden CLS cause.

RPM lift seen: indirect — CLS under 0.1 protects rankings and session depth.

Pros: ranking + RPM both win. Cons: reserved space looks empty on no-fill.

Lift: ★★★☆☆ — Risk: ★☆☆☆☆
Best for: anyone whose CWV is amber/red. Skip if CLS is already green.