In order of impact: optimising images (WebP or AVIF formats, sizes adapted to the screen, lazy loading) removes 25 to 40% of total weight; reducing JavaScript saves 10 to 20%; a well-configured cache and a CDN cut repeat transfers by 30 to 60%; and a hosting provider in a country with low-carbon electricity and a low PUE can cut the data centre emission source by up to 80%. For a brochure site of a few pages, doing without a complex framework is often the clearest gain.
Read the source article: Website carbon footprint: how to calculate and reduce it