Next-generation image formats webP and AVIF are an easy win for WordPress sites to improve their performance, but which is better for performance?
TL/DR :: Use webP for better compatibility with browsers, Google Merchant and PSI Testing.
WebP, developed by Google and released in 2010, has been the go-to replacement for traditional JPEG and PNG formats for over a decade. It offers impressive compression efficiency with 25-34% smaller file sizes compared to JPEG at equivalent quality levels. On the other hand, AVIF (AV1 Image File Format) is the newer contender, released by the Alliance for Open Media in February 2019. Despite being relatively recent, AVIF delivers even more aggressive compression, typically producing files 30-50% smaller than WebP and up to 50% smaller than JPEG while maintaining superior image quality, particularly excelling with its support for 12-bit colour depth compared to WebP’s 8-bit limitation.
WebP enjoys widespread support across all major browsers since September 2020, with 96% browser compatibility as of 2025. AVIF, being newer, achieved full browser support more recently in January 2024, currently supporting 93% of web browsers. WordPress itself has embraced both formats, with WebP support added in version 5.8 and AVIF support introduced in WordPress 6.5. However, several known issues persist with both formats: WebP can suffer from color banding and blockiness in certain compression scenarios, while AVIF faces reliability challenges with PNG conversions and server configuration dependencies, particularly in shared hosting environments.
On this site, I started using uncompressed PNGs and JPEGs, resulting in a homepage size of up to 4MB. I then installed the Performance Lab plugin and switched to using AVIF, giving me a homepage size of 330KB. The Google Page Speed Insight score for desktop was around 97% but mobile scored 75% as the mobile test was reading PNGs. Switching to the slightly older but better supported webP format reduced the homepage size to 288 KB, and improved the PSI score for desktop to 100% and for mobile to 97%.
Another consideration is compatibility with services such as Google Merchant Centre. As of August 2025, Google Merchant Centre supports webP but not AVIF, making webP the better choice for WooCommerce shops.
Summary: Both AVIF and webP delivered significant improvements, but for compatibility, I am preferring webP.
Tech Stack
- GeneratePress Theme Pro with Starter Theme “Freelancer” and Generate Blocks Pro
- Performance Lab plugin – Modern Image Formats
- SiteGround Performance Optimisation. SiteGround is a good value choice for my site, but for busier sites & shops, I recommend BigScoots and Kinsta.
Can I Use?
GTMetrix
PageSpeed Insights (PSI)
