developer.mozilla.org

No JSON-LD blocks found. Add a <script type="application/ld+json"> with a schema.org type for this page.

Fix: Add a <script type="application/ld+json"> describing the page (Organization, Article, Product, FAQPage).

Found /llms.txt but missing H1 header and markdown links.

Fix: Publish /llms.txt at your domain root. Build a spec-compliant one at /tools/llms-txt-generator.

No HTTP Link: response headers. Emit canonical/alternate/describedby relations so HEAD-only or stream-rendering agents get them without parsing HTML.

Fix: Emit `Link:` headers for canonical, alternate-language, and describedby relations. Agents that fetch HEAD-only or stream-render rely on these.

Visible text is 5.3% of HTML weight (6382/121364 bytes). Low. Markup may be crowding out agent-usable text.

Fix: Heavy ad or navigation markup crowds out agent-usable text. Aim for a text-to-DOM ratio above 15%.

Page looks like Article|BlogPosting|NewsArticle; missing JSON-LD type(s): Article|BlogPosting|NewsArticle.

Fix: Align JSON-LD type to page purpose. Product pages without Product markup are skipped by agent shopping flows.

No Content-Signal directives. Add e.g. `Content-Signal: ai-train=no, ai-summarize=yes` to declare granular AI usage policy beyond binary allow/disallow.

Fix: Add `Content-Signal:` directives to your robots.txt. This is the emerging standard (Cloudflare-driven) for declaring fine-grained AI usage policy beyond a binary allow/disallow.

# MDN Web Docs

> The MDN Web Docs site provides information about Open Web technologies including HTML, CSS, and APIs for both Web sites and progressive web apps.

## Key pages
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- [Resources for Developers, by Developers](https://developer.mozilla.org/)
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- [Latest news](https://developer.mozilla.org/)
- [Recent contributions](https://developer.mozilla.org/)
- [Contributor Spotlight](https://developer.mozilla.org/)

## About
Describe what developer.mozilla.org does, who it's for, and the primary action you want an
agent to be able to complete. Keep it factual and current.

MDN Web Docs Skip to main content Skip to search HTML HTML: Markup language HTML reference Elements Global attributes Attributes See all… HTML guides Responsive images HTML cheatsheet Date & time formats See all… Markup languages SVG MathML XML CSS CSS: Styling language CSS reference Properties Selectors At-rules Values See all… CSS guides Box model Animations Flexbox Colors See all… Layout cookbook Column layouts Centering an element Card component See all… JavaScript JS JavaScript: Scripting language JS reference Standard built-in objects Expressions & operators Statements & declarations Functions See all… JS guides Control flow & error handing Loops and iteration Working with objects Using classes See all… Web APIs Web APIs: Programming interfaces Web API reference File system API Fetch API Geolocation API HTML DOM API Push API Service worker API See all… Web API guides Using the Web animation API Using the Fetch API Working with the History API Using the Web speech API Using web workers All All web technology Technologies Accessibility HTTP URI Web extensions WebAssembly WebDriver See all… Topics Media Performance Privacy Security Progressive web apps Learn Learn web development Frontend developer course Getting started modules Core modules MDN Curriculum Check out the video course from Scrimba, our partner Learn HTML Structuring content with HTML module Learn CSS CSS styling basics module CSS layout module Learn JavaScript Dynamic scripting with JavaScript module Tools Discover our tools Playground HTTP Observatory Border-image generator Border-radius generator Box-shadow generator Color format converter Color mixer Shape generator About Get to know MDN better About MDN Advertise with us Community MDN on GitHub Blog MDN Theme OS default Light Dark English (US) Remember language Learn more Deutsch English (US) Español Français 日本語 한국어 Português (do Brasil) Русский 中文 (简体) 正體中文 (繁體) Resources for Developers, by Developers Documenting CSS , HTML , and JavaScript , since 2005. Search Featured articles Blog Celebrating 20 years of MDN MDN turns 20! Let's look at how we started, how MDN became the most trusted resource for web developers, the impact it's had on the open web, and yes, there's cake, too. Web APIs Navigation API The Navigation API provides the ability to initiate, intercept, and manage browser navigation actions. It can also examine an application's history entries. This is a successor to previous web platform features such as the History API and window.location, which solves their shortcomings and is specifically aimed at the needs of single-page applications (SPAs). Web APIs Trusted Types API The Trusted Types API gives web developers a way to ensure that input has been passed through a user-specified transformation function before being passed to an API that might execute that input. This can help to protect against client-side cross-site scripting (XSS) attacks. Most commonly the transformation function sanitizes the input. CSS Using CSS anchor positioning The CSS anchor positioning module defines features that allow you to tether elements together. Elements can be defined as anchor elements and anchor-positioned elements. Anchor-positioned elements can be bound to anchor elements. The anchor-positioned elements can then have their size and position set relative to the size and location of the anchor elements to which they are bound. Latest news developer.mozilla.org Introducing the MDN MCP server 1 month ago MDN's MCP server brings MDN's documentation and browser compatibility data directly into your editor or IDE, giving your LLM or coding agent access to accurate, up-to-date web platform information. developer.mozilla.org Under the hood of MDN's new frontend 4 months ago You may have spotted that MDN has a new frontend. There's plenty happening under the surface, so let's unpack the technologies we chose, the architectural decisions we made, and why we did a rebuild at all. developer.mozilla.org Image formats: Codecs and compression tools 9 months ago Image compression involves countless trade-offs between quality, size, and speed. In this final part of the series, we experiment with codecs, metrics, and tools to find practical ways to balance efficiency and visual fidelity. developer.mozilla.org A beginner-friendly guide to view transitions in CSS 10 months ago Learn how to bring smooth, animated navigation to multi-page apps with view transitions. With just one line of CSS, you can enable seamless transitions between pages. Recent contributions mdn/translated-content 1 day ago [es] fixes object typo mdn/translated-content 1 day ago Sync es API constructor subpage template with English source mdn/translated-content 1 day ago [es] docs: add contributor guide sections on links, GFM callouts, macros, and writing style mdn/content 12 hours ago Update Wasm SIMD bitwise instruction pages to display BCD and specs mdn/content 12 hours ago Update Wasm definitions pages to display BCD and specs mdn/content 12 hours ago Update Wasm exception handling instruction pages to display BCD and s… mdn/content 11 hours ago Update CODEOWNERS: rectify order mdn/translated-content 5 hours ago chore(fr): update experimentales features mdn/content 4 hours ago link parameters property & param() function mdn/translated-content 4 hours ago docs(es): add mariomorillo to the Spanish (es) review team Contributor Spotlight Shrinivass Arunachalam Balasubramanian MDN closely follows W3C standards which helps me keep up with important topics. It's a complete package as it caters to everything; complex APIs, new browser functionalities, and best practices. MDN serves as a truly valuable resource and continues to assist me in my everyday development. Get involved Your blueprint for a better internet. MDN About Blog Mozilla careers Advertise with us MDN Plus Product help Contribute MDN Community Community resources Writing guidelines MDN Discord MDN on GitHub Developers Web technologies Learn web development Guides Tutorials Glossary Hacks blog Website Privacy Notice Telemetry Settings Legal Community Participation Guidelines Portions of this content are ©1998–2026 by individual mozilla.org contributors. Content available under a Creative Commons license .

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