Frontend guide
How the Browser Works: From URL to Pixels
A plain-English guide to what the browser actually does with your code — fetching HTML and building the DOM, parsing CSS into the CSSOM and the render tree, computing layout, painting and compositing pixels, the single-threaded event loop that keeps pages responsive, and the reflow/repaint costs behind real web performance and Core Web Vitals.
6 lessons·53 min read·Free, no account
- 01What Happens When You Open a Web PageBeginner·8 min
- 02The DOM: How the Browser Models a PageBeginner·9 min
- 03CSS and the Render TreeIntermediate·9 min
- 04Layout, Paint, and CompositeIntermediate·9 min
- 05The Event Loop: How Pages Stay ResponsiveIntermediate·9 min
- 06Reflows, Repaints, and Making Pages FastAdvanced·9 min