Iframe dimensions set
Whether iframes declare dimensions - unsized iframes shift layout.
At a glance the headline numbers for Iframe dimensions set
Whether iframes declare dimensions - unsized iframes shift layout.
68.4% of iframes declare no dimensions.
The iframe dimensions set mix who uses what, and how fast each group loads
Iframe dimensions set. On the fleet: 68.4% has none, 31.6% has dimensions. 35.4% of sites use at least one has_none.
Lowest-share bucket: INP 46ms. Highest-share bucket: INP 54ms. r = +0.30.
Passing INP per bucket every category and count level at once - color is the pass rate
Each row is a category, each column its own count bucket (few on the left, many on the right); the cell is the share of those sites passing INP.
No category moves the INP pass rate much, however many a site ships. computed
Few vs many - does quantity cost INP? the pass rate with few vs many of each category
Per category: the pass rate among pages with FEW of it (hollow ring) against pages with MANY (solid dot), worst trend first. Thin buckets are excluded from the endpoints.
More Has none costs the most: the INP pass rate falls from 99% with few to 99% with many. computed
Why this matters for the Core Web Vitals, and where to start fixing it
An iframe without dimensions is a box of unknown size. The browser guesses, the embed loads, the box resizes, and everything below it jumps. That is the CLS pattern for embeds: maps, videos, forms, ads.
Reserve the slot. Width and height (or aspect-ratio on the container) make the size known before the content arrives, and the late embed lands without moving anything.
How does this affect the Core Web Vitals?
Passing CLS barely moves across the range: 80% at one end, 76% at the other. This signal does not separate passing sites from failing ones.
Chrome field data from 94,910 sites, representing millions of real page loads. How we measured.