- Back/forward cache
The back/forward cache (bfcache) is a browser optimization that keeps a complete snapshot of a page in memory when a user navigates away.
- Compression (Gzip/Brotli)
HTTP compression is the process of shrinking text files such as HTML, CSS and JavaScript on the server before they travel over the network.
- Critical CSS
Critical CSS is the CSS needed to render the content that is visible without scrolling (above the fold).
- DOM size
DOM size is the total number of elements in the Document Object Model of a web page, the in-memory tree the browser builds from the HTML.
- fetchpriority
fetchpriority is an HTML attribute that tells the browser how important a resource is compared to other resources of the same type.
- Minification
Minification is the process of removing unnecessary or redundant data from a resource without changing how the browser processes it (MDN).
- Preload / preconnect
Preload, preconnect and prefetch are resource hints.
- Speculation Rules API
The Speculation Rules API lets a web page tell the browser which URLs a visitor will probably open next.
- Third-party scripts
Third-party scripts are JavaScript files that a website loads from domains it does not control.
- Web font loading
Web font loading describes how a page fetches custom font files and what the browser shows while they download.