The Web Developer Guide provides useful how-to content to help you actually use Web technologies to do what you want or need to do.

Tutorials to take you step-by-step through learning HTML, CSS, JavaScript, and Web APIs.

Enabling as many people as possible to use websites, even when those people's abilities are limited in some way.

Making content as available and interactive as possible, as soon as possible.

Protecting users' personal data.

Protecting users from data leaks and data theft, side-channel attacks, and attacks such as cross-site scripting, content injection, and click-jacking.

Definitions of Web-related terms.

JavaScript programming APIs you can use to build apps on the Web.

HTML provides the fundamental building blocks for structuring Web documents and apps.

Cascading Style Sheets are used to describe the appearance of Web documents and apps.

JavaScript is the Web's native programming language.

WebAssembly allows programs written in C, C++, Rust, Swift, C#, Go, and more to run on the Web.

Events are what you build Web apps to react to; for example, when a Web page finishes loading, or a user selects something, presses a key, resizes a window, submits a form, or pauses a video.

HTTP is the fundamental Internet protocol for fetching documents, stylesheets, scripts, images, videos, fonts, and other resources over the Web — and for sending data back to Web servers.

Formats, codecs, protocols, APIs, and techniques for embedding and streaming video, audio, and image content in Web documents and apps.

Scalable Vector Graphics lets you create images that scale smoothly to any size.

MathML lets you display complex mathematical notation on the Web.

Uniform Resource Identifiers are used by various technologies, including the browser itself via the address bar, to identify resources in various ways.

WebDriver is a browser-automation mechanism for remotely controlling a browser by emulating the actions of a real person using the browser. It's widely used for cross-browser testing of Web apps.

Web Extensions are a way for you to give users enhanced capabilities in their browsers — for doing things such as blocking ads and other content, customizing the appearance of pages, and more.

Web App Manifests let you enable users to install Web apps to their device home screens, with aspects such as portrait/landscape screen orientation and display mode (e.g., full screen) pre-set.

Progressive Web Apps provide a user experience similar to native mobile apps.

OpenSearch allows a website to describe a search engine for itself, so that a browser or other client application can use that search engine.

The Extensible Markup Language is a strict serialization of the Document Object Model.

Extensible Stylesheet Language Transformations is an XML-based language used, in conjunction with specialized processing software, for the transformation of XML documents.

XPath uses a non-XML syntax to provide a flexible way of addressing (pointing to) different parts of an XML document. It can also be used to test addressed nodes within a document to determine whether they match a pattern or not.

EXSLT a set of extensions to XSLT.

Documentation for the set of web-developer tools built into Firefox.

Documentation for the set of web-developer tools built into Chrome.

Documentation for the set of web-developer tools built into Safari.

Documentation for the set of web-developer tools built into Edge.