Web Performance Fundamentals

Web performance is the combined experience of how quickly a page appears, becomes usable, and responds to input. A fast website begins with a clear understanding of what the browser actually needs to download and execute.

Measure before optimizing

Use a production-like build and inspect real measurements before changing code. Network requests, JavaScript execution, image sizes, and layout shifts each point to different solutions. A guess can easily make a page more complicated without improving the user experience.

Treat images as part of the layout

Large images are often among the heaviest assets on a page. Choose an appropriate format, serve a size close to the rendered dimensions, and reserve space for the image so content does not jump while it loads.

Send less JavaScript

Every script has a download, parse, and execution cost. Prefer server-rendered content when interaction is not required, load optional features only when they are needed, and avoid shipping a large dependency for a small task.

Improve the slowest path first

Performance work is most effective when it targets the part users actually wait for. After each change, measure again and keep the improvement that helps the largest number of users. Small reductions in critical work often matter more than polishing code that is not on the initial path.