Use the most efficient file compression formats.
Easy to implement
13 High impact score
WebP and AVIF are the two formats you should choose from.
AVIF compresses better than webp, so is the preferable choice. However, it is not supported by all tools, although it is now supported by Safari (as of Sep 2022)
GIFs should never be used, and avoid using lossless PNGs as webp and AVIF support transparency.
Great tools to help with compression and conversion: