The Browser Platform
What is actually happening underneath the framework.
21 topics
The Critical Rendering Path
What the browser does between receiving HTML and painting a pixel, and which steps block each other.
core25 minThe DOM & CSSOM as APIs
What the DOM actually is, which operations are cheap, and the reading APIs that quietly force the browser to do work.
core20 minThe Event Model
Capture, target and bubble; delegation; passive listeners; and why stopPropagation is usually the wrong fix.
core25 minLayout Thrashing & Forced Reflow
The read-write-read loop that turns one layout into hundreds, how to spot it in a profile, and how to break it.
core20 minCompositing & GPU Layers
Why transform and opacity are cheap to animate, what promotes an element to its own layer, and how will-change becomes a memory leak.
core20 minThe Observer APIs
Intersection, Resize, Mutation and Performance observers — the callback-based replacements for polling the layout.
core20 minNavigation, History & bfcache
The History API, what makes a page ineligible for the back/forward cache, and why instant back navigation is worth protecting.
core20 minView Transitions & Soft Navigation
The platform API for animating between states and pages, and why it changes what SPA-style transitions cost.
deep20 minShadow DOM & Web Components
Real style and DOM encapsulation in the platform, what it costs in practice, and where it beats a React component.
deep25 minBrowser Storage
localStorage, sessionStorage, IndexedDB, cookies and the Cache API — what each is for, and what gets evicted.
core25 minHTTP Caching
Cache-Control, ETags and the two questions every response answers — can this be stored, and how do we know it is still good.
core25 minFetch, CORS & Credentials
Why the browser blocks a response it already received, what makes a request preflighted, and how credentials change the rules.
core25 minHTTP Versions & Transport
What HTTP/2 and HTTP/3 changed, which old optimisations they made harmful, and where head-of-line blocking actually lives.
core20 minRealtime Transports
WebSockets, SSE, long polling and WebTransport — choosing by direction, infrastructure and failure behaviour.
core20 minService Workers & Offline
A programmable proxy between the page and the network — the lifecycle that confuses everyone, and the strategies worth knowing.
deep25 minWeb Workers & Off-Main-Thread Work
Real parallelism in the browser, what it costs to move data across the boundary, and when it is the only fix.
core20 minFiles, Blobs & Streams
Getting bytes in and out of the browser — uploads, downloads, object URLs, and why streaming beats buffering.
core20 minImages & Media on the Web
Responsive images, modern formats, and the markup that decides whether the browser downloads the right bytes.
core20 minDevice & Permission APIs
Camera, geolocation, clipboard, notifications and the rest — the permission model they share, and how to ask without being denied.
deep20 minFeature Detection & Progressive Enhancement
Building so the core works everywhere and the nice parts activate where supported — without shipping polyfills nobody needs.
core20 minConcurrency Models
The four ways systems run more than one thing at once, and why JavaScript picked the one it did.
core25 minshared