The State of Web Vitals

Wix LCP image format and the Core Web Vitals

JPEG, WebP, PNG, AVIF, SVG, or GIF on the LCP image: how much each format weighs (32 KB on AVIF vs 140 KB on JPEG) and how that changes LCP.

Field data PhoneDesktopAll Scope All sites October 2026 edition · All devices field outcomes · Wix sites only
Wix Scoped to 5,623 sites out of 203,892 analyzed (cms) Compare with all sites →

On Wix, 1.1% of LCP images are still served as JPEG. WebP accounts for 0.1%, PNG for 0.3%, and AVIF for 98.2%. When the LCP image is AVIF, 94% of sites have a good LCP and 50% with WebP, against 90% for JPEG and 83% for PNG. Switching from JPEG to WebP or AVIF cuts median hero image transfer weight from 140 KB to 27 KB (WebP) and 32 KB (AVIF).

The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP pass rate

By LCP image format, Wix sites have a good LCP at AVIF at 94%. Within Wix, WebP and AVIF beat JPEG and PNG because smaller next-gen files finish downloading faster and reduce image load duration.

SitesGood, needs improvement, poor LCPMedian
All Wix sites5,33394%1.2s
AVIF 98.2%3,72294%1.2s
GIF 0.3%1292%1.2s
JPEG (jpg) 1.1%4190%1.3s
PNG 0.3%1283%937ms
WebP 0.1%250%829ms
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP image format usage

Images (<img> tags plus CSS background-image rules) are the LCP element on 71.5% of audited Wix sites. Across the 3,987 Wix sites with an image LCP element, JPEG serves 1.1%, WebP serves 0.1%, PNG serves 0.3%, AVIF serves 98.2%, and GIF serves 0.3%.

LCP element type across all audited sites 5,589 sites
<img> element 70.4%Text block 26.7%
Sites with an image LCP by image format 3,987 sites
AVIF 98.2%
AVIF 98.2% JPEG (jpg) 1.1% GIF 0.3% PNG 0.3% WebP 0.1%
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP image weight and pixel efficiency by format

AVIF serves the largest median rendered hero image (0.22 MP) at the smallest file size: 32 KB median (52 KB at p75), or 152 KB per megapixel. Median file size is 27 KB for WebP (1,695 KB/MP), 140 KB for JPEG (2,283 KB/MP), and 19 KB for PNG (0 KB/MP). Nearly half of all PNG (16.7%) and JPEG (35.7%) LCP images weigh over 200 KB, against 50.0% of WebP and 0.6% of AVIF.

Format Median (p50) and 75th percentile (p75) transfer weight KB / megapixel Over 200 KB
AVIF 3,917 32 KB p75 52 KB 152 KB/MP0.22 MP 0.6%
JPEG (jpg) 44 140 KB p75 287 KB 2,283 KB/MP0.11 MP 35.7%
Solid bar: median transfer weight (p50) Light bar: 50th to 75th percentile tail (p75)
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
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Resource load time and the four LCP phases by image format

Smaller image files reduce resource load duration: AVIF downloads in a median 139 ms, WebP in 79 ms, PNG in 135 ms, JPEG in 159 ms. AVIF and WebP sites also start with a faster Time to First Byte: 419 ms on AVIF and 284 ms on WebP, against 427 ms on JPEG. That gap comes from edge CDNs, which both convert images to modern formats and cache the HTML response.

Median LCP phase breakdown (Chrome field p75) Load duration Median LCP
Wix sites with an image LCP by image format 2,881421 ms459 ms139 ms153 ms139 ms1.2s
AVIF 2,830419 ms460 ms139 ms152 ms139 ms1.2s
JPEG (jpg) 32427 ms436 ms159 ms149 ms159 ms1.4s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP image format per framework

React serves AVIF on 98% of its image-LCP sites, and 94% of React sites have a good LCP.

FrameworkLCP image format on its sitesGood LCP
Wix sites with an image LCP by image format 3,987 sitesAVIF 98%94%
React 3,986 sitesAVIF 98%94%
AVIF JPEG (jpg) GIF PNG WebP
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
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Understanding LCP image format

Serve photographic LCP images as AVIF or WebP, and keep PNG for logos or flat graphics that need lossless pixels. You do not have to convert files by hand. An image CDN or a <picture> element with <source type="image/avif"> and <source type="image/webp"> lets each browser pick the smallest format it supports. Across this dataset, 1.1% of LCP images are still JPEG (140 KB median, 90% good LCP) and 0.3% are PNG (19 KB median, 83% good LCP). Switching to WebP (27 KB median, 50% good LCP) or AVIF (32 KB median, 94% good LCP) cuts median load time from 159 ms to 79 ms and 139 ms.

Go fix it Optimize images for Core Web Vitals → JPEG XL and Core Web Vitals → Optimize the LCP image →
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field data · 3,987 sites with an image LCP by image formatBy Arjen Karel · corewebvitals.io/state-of-cwv
Related signals LCP priority hint → LCP origin → LCP responsive markup → LCP discovery → By Arjen Karel · 5,621 crawled Wix sites (5,333 with all devices Chrome field data, 3,987 sites with an image LCP by image format, October 2026) · How we measured