Documentation · ESSENTIAL
MDN Web Docs
A dependable reference for HTML, CSS, JavaScript and the browser APIs that bring them together.
developer.mozilla.org THE WEB, WELL BOOKMARKED
Fill your creative toolkit.
98 references, libraries and tools for designing, building and testing the web.
13 resources · External links open in a new tab. Some services require an account or paid plan.
Compatibility · ESSENTIAL
Can I use
Check browser support before a promising experiment becomes a production dependency.
caniuse.comDocumentation · ESSENTIAL
MDN HTML reference
HTML elements, attributes, forms and document structure, with reference material and browser notes.
developer.mozilla.orgLibraries
CodeMirror
An extensible code editor for the browser, with language support and accessible editing controls.
codemirror.netTesting
Playwright
Automate browsers to test your important flows across current browser engines.
playwright.devDocumentation
HTML Living Standard
The maintained HTML specification from WHATWG, covering the language and browser processing rules.
html.spec.whatwg.orgLearning
The Modern JavaScript Tutorial
A structured path through JavaScript fundamentals, browser interaction and asynchronous programming.
javascript.infoPage testing
WebPageTest
Run detailed page-load tests and inspect timing, resource waterfalls and rendering behavior.
www.webpagetest.orgPage testing
Responsively
A desktop development browser for viewing a page across multiple responsive screen sizes.
responsively.appPage testing
Polypane
A development browser with responsive views and accessibility tools. Commercial plans are available.
polypane.appJavaScript tools
You Might Not Need jQuery
Compare common jQuery operations with browser-native JavaScript equivalents.
youmightnotneedjquery.comJavaScript tools
Transform
Convert between common code and data formats with focused browser-based utilities.
transform.toolsAsset tools
Squoosh
Compare image compression settings in the browser and export optimized image assets.
squoosh.app