I’ve been running my own crawler over the homepages of ~14.8M domains from Google’s Chrome UX Report list, and 34.4% of sites are self-hosted WordPress. I measured TTFB (from a European probe) and matched each site to its real-user Core Web Vitals data from CrUX.

A few insights:

1. Caching matters more than the theme. I compared the 10 most-used themes. Cached, they all respond in 267 to 355ms. Uncached, they range from 964ms (GeneratePress) to 1.9s (Woodmart).

Theme differences mostly only show up when there’s no cache. Meanwhile, 38.3% of WordPress sites have no caching I could detect.

2. Cache plugins depend on the server they were built for. On LiteSpeed servers, LiteSpeed Cache is among the best performers, but on non litespeed servers it’s worse than no cache at all. Similar results with Siteground’s SG optimiser plugin.

3. Page builders, by LCP pass rate (share of sites with a “good” Largest Contentful Paint):
ACF-based sites: 72%
Classic Editor: 68.8% (inferred from no block or builder markup)
Oxygen: 67.4%, Bricks: 66.2%
Gutenberg: 64.7%
WPBakery: 49.1%
Elementor: 44.5% (26% of WordPress sites)

4. CDN caching works best. When a CDN serves the page from its cache, 99.5% of WordPress sites respond in under 800ms. With a caching plugin it’s 77.9%, and with no caching at all it’s 36.6%.

Full WordPress report section, including the per-server cache plugin charts: https://theweb.report/#wordpress

If you run one of these setups and your experience doesn’t match, I’d love to hear it.

Site also has a free audit tool which baselines your site against the whole 14 million site corpus, hope it’s useful!