A free, self-paced textbook in 8 chapters. Read a chapter, then drill it with the 217 companion flashcards using spaced repetition.
Frontend performance describes how quickly and smoothly a web application loads, renders, and responds to a user's actions. It is not just about raw speed measured in the lab; it s...
To act on performance you have to understand the path the browser walks from bytes to pixels. The critical rendering path is the sequence in which the browser parses HTML, builds t...
The transport layer shapes perceived performance as much as anything in your application code. HTTP/2 introduced multiplexing so many requests share a single connection without hea...
Images are usually the heaviest assets on a page, and they are also the assets most directly tied to perceived speed and layout stability. Three choices matter: format, size, and l...
The fastest JavaScript is the JavaScript you never ship, and the rest of the bundle should still be smaller than you think. A practical strategy splits code into three categories:...
CSS affects performance in two distinct ways: bytes over the wire and work on the main thread. The bytes come from unused rules shipped because removing them by hand is tedious. To...
Once the page is loaded, the metric that matters is INP, which captures how long users wait between an interaction and the visible response. INP is bottlenecked by main-thread work...
Where you render matters as much as how you render. Server-side rendering produces meaningful HTML before client-side JavaScript finishes, which improves LCP and SEO at the cost of...