The State of Web Vitals

HTTP cache TTL tiers (immutable, long TTL, no-store) and the Core Web Vitals

Unspecified cache headers (97.6%), long TTLs (74.1%), medium TTLs (73.6%), no-store (67.7%), short TTLs (67.7%), no-cache (39.4%), and Cache-Control: immutable (26.1%).

Field data PhoneDesktopAll Scope All sites October 2026 edition · Phone field outcomes

26.1% of sites use Cache-Control: immutable HTTP cache TTL tiers, and 83% of those sites have a good LCP, against 82% of all sites.

The State of Web Vitals · October 2026 · 210,902 crawled sites · 126,761 with phone field data · 206,252 sites with HTTP cache TTL tiersBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP pass rate

Sites with Cache-Control: immutable HTTP cache TTL tiers have a good LCP most often: 83%, against 82% of all sites. Sites with short-TTL cache tiers have it least often, at 81%.

SitesGood, needs improvement, poor LCPMedian
All sites126,76182%1.6s
Cache-Control: immutable 26.1%35,42083%1.6s
Unspecified cache lifetime 97.6%123,84282%1.6s
Medium TTL (1 - 30 days) 73.6%94,12881%1.6s
Long TTL (> 30 days) 74.1%93,87181%1.6s
Cache-Control: no-cache 39.4%52,27881%1.6s
Cache-Control: no-store 67.7%86,91181%1.6s
Short TTL (< 1 day) 67.7%87,24481%1.6s
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · 210,902 crawled sites · 126,761 with phone field data · 206,252 sites with HTTP cache TTL tiersBy Arjen Karel · corewebvitals.io/state-of-cwv
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HTTP cache TTL tiers usage

Unspecified cache is the most used: 97.6% of sites. Cache-Control: immutable is 26.1% of sites.

Sites using each option (sites can use more than one) 206,252 sites
Unspecified cache lifetime 97.6% Long TTL (> 30 days) 74.1% Medium TTL (1 - 30 days) 73.6% Cache-Control: no-store 67.7% Short TTL (< 1 day) 67.7%
Unspecified cache lifetime 97.6% Long TTL (> 30 days) 74.1% Medium TTL (1 - 30 days) 73.6% Cache-Control: no-store 67.7% Short TTL (< 1 day) 67.7% Cache-Control: no-cache 39.4% Cache-Control: immutable 26.1%
The State of Web Vitals · October 2026 · 210,902 crawled sites · 126,761 with phone field data · 206,252 sites with HTTP cache TTL tiersBy Arjen Karel · corewebvitals.io/state-of-cwv
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How HTTP cache TTL tiers affect the four LCP phases

Across the four LCP sub-parts in Chrome's field data, the largest gap between Cache-Control: immutable and short-TTL sits in time to first byte (TTFB): 552 ms median for Cache-Control: immutable against 657 ms for short-TTL. Overall median field LCP is 1.6s for Cache-Control: immutable (TTFB 552 ms, load delay 426 ms, load duration 159 ms, render delay 253 ms) versus 1.6s for short-TTL.

Median LCP phase breakdown (Chrome field p75) Load delay Median LCP
Sites with HTTP cache TTL tiers 92,464650 ms336 ms236 ms336 mslab 326 ms1.6s
Unspecified cache lifetime 90,565653 ms338 ms236 ms338 mslab 328 ms1.6s
Medium TTL (1 - 30 days) 69,868653 ms349 ms244 ms349 mslab 340 ms1.6s
Cache-Control: no-store 65,321653 ms354 ms242 ms354 mslab 344 ms1.6s
Long TTL (> 30 days) 69,793655 ms357 ms244 ms357 mslab 347 ms1.6s
Short TTL (< 1 day) 65,383657 ms358 ms247 ms358 mslab 347 ms1.6s
Cache-Control: no-cache 39,835632 ms381 ms156 ms249 ms381 mslab 374 ms1.6s
Cache-Control: immutable 27,402552 ms426 ms159 ms253 ms426 mslab 419 ms1.6s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · 210,902 crawled sites · 126,761 with phone field data · 206,252 sites with HTTP cache TTL tiersBy Arjen Karel · corewebvitals.io/state-of-cwv
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Understanding HTTP cache TTL tiers

How Cache-Control: immutable and long TTLs accelerate repeat views

Field Core Web Vitals combine first visits and repeat navigations from Chrome users. Sites that serve content-hashed static bundles with Cache-Control: immutable (26.1% of sites) achieve 83% good field LCP (1.6s median LCP), outperforming sites limited to short TTLs (67.7%, 81% good LCP) or no-store responses (67.7%, 81% good LCP).

Fingerprint static CSS, JavaScript, and font filenames and serve them with Cache-Control: public, max-age=31536000, immutable. While 74.1% of sites use long cache TTLs, only 26.1% include the immutable directive (83% good LCP), which prevents unnecessary 304 revalidation round-trips when users reload or navigate across pages.

Go fix it TTFB: cache duration → Configure Cloudflare for passing the Core Web Vitals →
The State of Web Vitals · October 2026 · 210,902 crawled sites · 126,761 with phone field data · 206,252 sites with HTTP cache TTL tiersBy Arjen Karel · corewebvitals.io/state-of-cwv
Platform & Framework Takeaways

How HTTP cache TTL tiers plays out per platform

What the field data shows when you isolate a single CMS or framework.

WordPress 65,509 sites
80.2% vs 16.1% long TTL vs Cache-Control: immutable

16.1% of WordPress sites serve Cache-Control: immutable assets, while 80.2% use long TTLs.

WordPress core appends a ?ver= query string to enqueued scripts and styles with wp_enqueue_script(). Across WordPress, 80.2% of sites serve long-TTL static files and 16.1% emit Cache-Control: immutable.

Read the WordPress cache strategy breakdown →
React & Next.js 9,570 sites
70.7% immutable hashed chunks (90% good LCP)

70.7% of React & Next.js sites serve Cache-Control: immutable assets (90% good LCP).

Across React sites, 70.7% emit Cache-Control: immutable headers on static chunks (90% good LCP) compared with 79% on short-TTL sites.

Related signals Cacheable responses → HTTP protocol mix → HTML size (kB) → Last-Modified present → By Arjen Karel · 210,902 crawled sites (126,761 with phone Chrome field data, 206,252 sites with HTTP cache TTL tiers, October 2026) · How we measured