JPG vs WebP vs Avif – WordPress Site Speed Optimization Test

This is a simple WordPress site speed benchmark test I ran to get some real hard numbers on how different image formats impact site speed, I am sure you can find this data elsewhere on the internet, but I am the type that has to have first hand experience, so I ran these benchmarks myself, I ran the test a total of 7 times using LightHouse in the browser web developer tools. I hope you find it useful!

Benchmark notes: I ran the tests on my local machine using WP Local. The sites were fresh with only Elementor installed. The two sites using the webp and avif formats also had the Performance Lab plugin activated plus the Performance Lab Modern Image Formats Module activated. No other plugins were installed on the sites. The theme was the default 2024 WordPress theme. I tested on a fresh Elementor page using the Basic Gallery widget with 201 images. I uploaded the same images to all three sites, all images were jpg’s, on two sites I installed Performance Lab and converted the jpg’s to webp’s and avif’s on site. In the end I had one site with 201 jpg images, 1 site with 201 avif images, and 1 site with 201 webp images. 

Additional notes: There were many uncontrolled variables during the test including various other processes running on my local machine including my browser etc. OS is Linux Mint 21.2 Cinnamon. Processor was a Intel© Xeon© CPU W3530 @ 2.80GHz × 4. Memory was 11.7 GiB. Graphics was NVIDIA Corporation GP107 [GeForce GTX 1050].