At a glance the headline numbers for HTTP protocol mix
The HTTP protocol carrying each request: h1, h2, h3.
34.2% of requests travel over HTTP/3. 10.6% still use HTTP/1.1.
The HTTP protocol mix mix who uses what, and how stable each group is
HTTP protocol mix. On the fleet: 55.2% h2, 34.2% h3, 10.6% http/1.1. 94.4% of sites use at least one h2.
Passing CLS 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 CLS.
H2 swings the hardest: 82% of sites pass CLS with few, 70% with many. computed
Few vs many - does quantity cost CLS? 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 H2 costs the most: the CLS pass rate falls from 82% with few to 70% with many. computed
Why this matters for the Core Web Vitals, and where to start fixing it
HTTP/1.1 gives you a handful of parallel requests per domain and queues the rest. HTTP/2 multiplexes any number of requests over one connection. HTTP/3 keeps that and removes the last stall: on HTTP/2 a single lost packet blocks every stream on the connection, on HTTP/3 only the stream that lost it.
A modern protocol also amplifies consolidation. The fewer domains you use, the more requests share one warm HTTP/3 connection. Requests still travelling over HTTP/1.1 are queueing for no reason.
How does this affect the Core Web Vitals?
The choice barely moves the LCP: 86% pass at best, 85% at worst. 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.