Image formats on React sites

Sites with AVIF images page image format mix have a good LCP most often: 90%, against 79% of all React sites. Sites with WebP images image formats have it least often, at 71%.

GIF images is the most used: 75.0% of React sites. AVIF images is 63.4% of React sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between AVIF images and WebP images sits in time to first byte (TTFB): 377 ms median for AVIF images against 959 ms for WebP images. Overall median field LCP is 1.3s for AVIF images (TTFB 377 ms, load delay 482 ms, load duration 235 ms, render delay 147 ms) versus 1.8s for WebP images.

Wix sets the page image format mix to AVIF images on 100% of its sites, and 92% of Wix sites have a good LCP, against 79% of all sites. WordPress sets the page image format mix to JPEG images on 87% of its sites, and 66% of WordPress sites have a good LCP.

PlatformPage image format mix on its sitesGood LCP

React sites with page image format mix 9,561 sitesGIF images / beacons 75%SVG vector graphics 69%AVIF images 63%PNG images 54%JPEG images 45%WebP images 25%Other image formats 22%79%

Wix 5,822 sitesAVIF images 100%GIF images / beacons 98%SVG vector graphics 69%PNG images 37%JPEG images 24%Other image formats 16%92%

WordPress 2,342 sitesJPEG images 87%PNG images 86%SVG vector graphics 73%WebP images 49%GIF images / beacons 39%Other image formats 25%66%

GIF images / beacons SVG vector graphics AVIF images PNG images JPEG images WebP images Other image formats

Does the platform explain the page image format mix difference?

Almost every site with AVIF images page image format mix is a Wix site, and almost every Wix site has AVIF images page image format mix, so the data can't tell AVIF images page image format mix and Wix apart. On WordPress, 61% of sites with GIF images page image format mix have a good LCP, against 65% of WordPress sites with SVG images. Within WordPress, sites with GIF images and SVG images have a good LCP about equally often.

How AVIF and WebP across the page cut transfer weight and free bandwidth for LCP

Even when the LCP element itself is optimized, legacy PNG and JPEG assets elsewhere in the viewport compete for bandwidth on the same connection. Across 6,057 sites (63.4%) serving AVIF images, 90% pass field LCP (1.2s median). WebP is present on 25.4% of sites (71% good LCP), whereas legacy PNG (54.4%, 74% good LCP) and JPEG (44.6%, 74% good LCP) remain on four out of five pages.