Compression, cookies, caching, redirects, crawling, and SSL
HTTP/2, persistent connections, origin settings, edge node caching
Code flow, out-dated libraries, slow loops or poor DOM interaction.
CSS and Web Fonts
Critical path rendering, selectors, style declarations, font format optimizations.
Lossless optimizations, smart lossy optimizations, WebP, Progressive JPEGs, favicons.
Mobile and Tablet
Responsive design, platform specific issues.
Streaming and seeking, MP4, WebM, bitrate and profile settings, animated GIFs.
Bloated ads, single-point-of-failure, blocking JS, API dysfunction.