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, 72% of sites have a good LCP and 72% with WebP, against 69% for JPEG and 66% 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 SVG at 72%, AVIF at 72%, GIF at 72%, WebP at 72%, JPEG at 69%, PNG at 66%. 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 156 ms, WebP in 161 ms, PNG in 204 ms, JPEG in 194 ms. AVIF and WebP sites also start with a faster Time to First Byte: 1117 ms on AVIF and 1099 ms on WebP, against 1142 ms on JPEG. That gap comes from edge CDNs, which both convert images to modern formats and cache the HTML response.
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%69%
Vue 3,455 sitesJPEG (jpg) 59%WebP 24%PNG 14%67%
React 1,582 sitesJPEG (jpg) 56%WebP 25%PNG 16%63%LCP image format or the framework
Does the framework explain the AVIF and WebP pass rate?
On jQuery, 71% of sites with a WebP LCP image and 71% with AVIF have a good LCP, compared with 68% for JPEG and 65% for PNG. Within jQuery, serving WebP instead of JPEG lifts the pass rate by 3 percentage points and beats PNG by 6 percentage points. On Vue, 71% of sites with a WebP LCP image have a good LCP, compared with 66% for JPEG and 66% 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 156 ms. WebP needs 351 KB/MP (161 ms load time), JPEG needs 657 KB/MP (194 ms load time), and lossless PNG needs 1,463 KB/MP (204 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, 69% good LCP) and 16.2% are PNG (215 KB median, 66% good LCP). Serving WebP (75 KB median, 72% good LCP) or AVIF (49 KB median, 72% good LCP) cuts median resource load time from 194 ms to 161 ms and 156 ms.
By Arjen Karel · 63,295 crawled WordPress sites (36,524 with phone Chrome field data, 43,647 sites with an image LCP by image format, October 2026). How we measured.