Fewer than half of websites give mobile visitors a good experience by Google's own measure, according to the performance chapter of the HTTP Archive's 2025 Web Almanac, published on 15 January 2026 and last updated on 5 May 2026. It found that 48% of websites passed all three Core Web Vitals on mobile and 56% on desktop, based on real-user data from July 2025. For UK websites, the findings point to a familiar weak spot: slow-loading main images on phones.
Key takeaways
- The 2025 Web Almanac found 48% of websites passed all three Core Web Vitals on mobile and 56% on desktop.
- LCP is the weak spot, with only 62% of sites achieving a good LCP on mobile, the lowest of the three metrics.
- Around 16-17% of pages lazy-load their LCP image, so never lazy-load the main above-the-fold image.
- The figures are global, as the report gives no UK breakdown, so treat them as a benchmark rather than a UK measurement.
What the Web Almanac found
The Web Almanac is an annual report by the HTTP Archive, a community project that tests millions of websites. Its performance chapter combines lab tests with field data from the Chrome UX Report (CrUX), which records how real Chrome users experience each site.
A site passes Core Web Vitals when, at the 75th percentile of visits, it meets all three targets: Largest Contentful Paint (LCP) within 2.5 seconds, Interaction to Next Paint (INP) of 200 milliseconds or less, and Cumulative Layout Shift (CLS) of 0.1 or less.
The pass rate keeps rising, but slowly:
| Year | Mobile pass rate | Desktop pass rate |
|---|---|---|
| 2021 | 32% | 41% |
| 2022 | 31% | 44% |
| 2023 | 36% | 48% |
| 2024 | 44% | 55% |
| 2025 | 48% | 56% |
Mobile improved by four points year on year, while desktop gained just one point.
LCP is the metric holding most sites back:
| Metric (2025) | Good on mobile | Good on desktop | Poor on mobile |
|---|---|---|---|
| Largest Contentful Paint | 62% | 74% | 13% |
| Interaction to Next Paint | 77% | 97% | 3% |
| Cumulative Layout Shift | 81% | 72% | 9% |
| Time to First Byte | 44% | 55% | 17% |
Only 62% of sites achieved a good LCP on mobile, the lowest of the three Core Web Vitals. INP on mobile improved from 74% in 2024 to 77%, and server response (TTFB, not a Core Web Vital but a big influence on LCP) remained weak, with only 44% of mobile sites rated good.
Why LCP is still slow
The chapter's detail explains a lot of the problem:
- The LCP element is an image on 76% of mobile pages and 85% of desktop pages.
- Around 16-17% of pages lazy-load their LCP image, which delays the most important image on the page.
- Only about 17% of pages use
fetchpriority="high"on the LCP image, and around 2% preload it. - JPG still accounts for 57% of LCP images and PNG for 26%. WebP has risen to 11%, while AVIF is under 1%.
- Only 44% of mobile LCP images are served from the same host as the page.
On the back/forward cache, which lets browsers restore pages instantly when users press Back, 23% of sites send Cache-Control: no-store, up from 21% in 2024. This header can stop pages being eligible for that cache.
What this means for UK businesses
The Web Almanac does not publish a country breakdown, and we could not find a robust, published UK-only Core Web Vitals pass rate, so treat the global figures as a benchmark rather than a UK measurement. Still, the patterns it describes are the ones we see on UK small-business sites: hero images on WordPress and Shopify themes, slider plugins, and shared hosting with slow server response.
Google says Core Web Vitals, along with other page experience aspects, align with "what our core ranking systems seek to reward", and it "highly recommend[s]" good scores. Good scores do not guarantee rankings, and relevant content matters more. But when competing UK businesses offer similar content, a page that loads quickly on a phone is more likely to keep a visitor who arrived from a search, an ad or a social post.
Because CrUX uses real Chrome visits, a site's own field data reflects its own audience. A UK business whose customers mostly browse on mid-range phones over mobile data may see weaker field results than a lab test on a fast office connection suggests.
What to do now
- Check your field data first. Run a free website audit on MakeItFlow. It pulls PageSpeed Insights and Lighthouse results, including Core Web Vitals, alongside SEO, DNS, email and security checks. Our guide to PageSpeed Insights scores explains field versus lab data.
- Fix the LCP image. Never lazy-load the main above-the-fold image, add
fetchpriority="high"to it, and serve it from your own domain or a fast CDN. See improving Largest Contentful Paint. - Modernise image formats. Convert large JPG and PNG hero images to WebP or AVIF and size them correctly. Our WebP and AVIF guide covers the options.
- Cut server response time. Use page caching, a CDN or better hosting to bring TTFB down. Read reducing TTFB.
- Reduce heavy JavaScript that delays interactions on mobile, particularly third-party chat widgets, sliders and tag managers.
- Review Cache-Control: no-store. Use it only on pages that genuinely need it, such as account or checkout pages, so other pages can benefit from the back/forward cache.
- Track progress over time. CrUX field data uses a rolling 28-day window, so improvements take weeks to show. MakeItFlow paid plans add scheduled re-scans and history, so you can see whether changes are working.
Frequently asked questions
Is the 48% figure for UK websites?
No. It is a global figure from the HTTP Archive's 2025 Web Almanac, using Chrome UX Report data from July 2025. The report does not provide a UK-specific breakdown.
Which Core Web Vital should a small business fix first?
For most sites, LCP. It has the lowest pass rate on mobile (62%), and the most common causes, such as an oversized or lazy-loaded hero image, are often quick to fix.
How long until improvements show up in Google's data?
Core Web Vitals field data is based on the previous 28 days of real Chrome visits, so expect around four weeks before a fix is fully reflected. Lab tools like Lighthouse show the effect immediately.
Related reading
- Chrome Adds Ad Metrics to CrUX: What Publishers Should Know: Chrome added four experimental ad metrics to CrUX on 15 September 2026. What ad count, density and weight mean for your site, and whether they affect rankings.
- Why Is My Website So Slow? Common Causes and How to Fix Them: Why is my website slow? Usually slow hosting, heavy images, too much JavaScript or third-party scripts. Find the real cause in minutes and fix it in order.
Sources
Written by the MakeItFlow team
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