WordPress LCP image format and the Core Web Vitals
JPEG, WebP, PNG, AVIF, SVG, or GIF on the LCP image: how much each format weighs (49 KB on AVIF vs 172 KB on JPEG) and how that changes LCP.
On WordPress, 60.6% of LCP images are still served as JPEG. WebP accounts for 20.8%, PNG for 16.2%, and AVIF for 0.7%. When the LCP image is AVIF, 79% of sites have a good LCP and 75% with WebP, against 76% for JPEG and 72% for PNG. Switching from JPEG to WebP or AVIF cuts median hero image transfer weight from 172 KB to 75 KB (WebP) and 49 KB (AVIF).
LCP pass rate
By LCP image format, WordPress sites have a good LCP at AVIF at 79%, JPEG at 76%, WebP at 75%, SVG at 74%, PNG at 72%. Within WordPress, WebP and AVIF beat JPEG and PNG because smaller next-gen files finish downloading faster and reduce image load duration.
LCP image format usage
Images (<img> tags plus CSS background-image rules) are the LCP element on 77.7% of audited WordPress sites. Across the 43,647 WordPress sites with an image LCP element, JPEG serves 60.6%, WebP serves 20.8%, PNG serves 16.2%, AVIF serves 0.7%, SVG serves 1.4%, and GIF serves 0.3%.
LCP image weight and pixel efficiency by format
AVIF serves the largest median rendered hero image (0.12 MP) at the smallest file size: 49 KB median (113 KB at p75), or 225 KB per megapixel. Median file size is 75 KB for WebP (351 KB/MP), 172 KB for JPEG (657 KB/MP), and 215 KB for PNG (1,463 KB/MP). Nearly half of all PNG (51.2%) and JPEG (45.7%) LCP images weigh over 200 KB, against 21.2% of WebP and 13.0% of AVIF.
Resource load time and the four LCP phases by image format
Smaller image files reduce resource load duration: AVIF downloads in a median 113 ms, WebP in 117 ms, PNG in 147 ms, JPEG in 136 ms.
LCP image format per framework
jQuery still serves JPEG on 61% and PNG on 16% of its sites, with WebP at 21%.
jQuery 41,723 sitesJPEG (jpg) 61%WebP 21%PNG 16%75%
Vue 3,455 sitesJPEG (jpg) 59%WebP 24%PNG 14%75%
React 1,582 sitesJPEG (jpg) 56%WebP 25%PNG 16%66%LCP image format or the framework
Does the framework explain the AVIF and WebP pass rate?
On jQuery, 74% of sites with a WebP LCP image and 77% with AVIF have a good LCP, compared with 76% for JPEG and 72% for PNG. On Vue, 73% of sites with a WebP LCP image have a good LCP, compared with 74% for JPEG and 74% for PNG.
Why image format changes resource load time, not load delay
An LCP image spends time in four stages: Time to First Byte, resource load delay, resource load time, and element render delay. The image format only touches resource load time, the window between the first and last byte of the image file. At the median resolution in this dataset, AVIF packs a megapixel into 225 KB/MP and finishes downloading in 113 ms. WebP needs 351 KB/MP (117 ms load time), JPEG needs 657 KB/MP (136 ms load time), and lossless PNG needs 1,463 KB/MP (147 ms load time). Because PNG is lossless, photographic hero banners saved as PNG blow up to 753 KB at the 75th percentile.
Understanding LCP image format
WordPress has generated WebP uploads natively since 5.8 and AVIF since 6.5 (when the server's Imagick or GD library supports it), or you can convert existing uploads with Performance Lab's Modern Image Formats plugin, ShortPixel, Imagify, or Cloudflare Polish. On WordPress, 60.6% of LCP images are still JPEG (172 KB median, 76% good LCP) and 16.2% are PNG (215 KB median, 72% good LCP). Serving WebP (75 KB median, 75% good LCP) or AVIF (49 KB median, 79% good LCP) cuts median resource load time from 136 ms to 117 ms and 113 ms.
By Arjen Karel · 63,295 crawled WordPress sites (17,005 with desktop Chrome field data, 43,647 sites with an image LCP by image format, October 2026). How we measured.