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MDN MCP Server

Official
MDN's official experimental MCP server for web search, docs, and browser compatibility data
How to install ↓ Compare GitHub source repository ↗
Category
Dev Tools #219 of 438
Stars
★ 191 Popular
Transport
Streamable HTTP
Runtime
Node.js · Hosted (no local runtime)
Credentials
No credential needed
License
MPL-2.0
Last commit
53FMRS · D

The MDN MCP server is an official Mozilla-maintained experimental project giving coding agents authoritative, current web platform docs and compatibility data, but it currently discloses limited details (no public tool list) and is explicitly labeled experimental, subject to change or withdrawal at any time.

Strongest · Setup experience 12/20 Weakest · Reliability 8/20

Reliability
8/20
Security and permissions
12/20
Maintenance
10/20
Documentation
11/20
Setup experience
12/20
Why each score
Reliability 8/20
The README provides a remote connection command and a local `npm install && npm start` flow, but no server manifest was available (marked 'not cached'), so the tool list, initialization handshake, and whether declared tools match real behavior cannot be verified. The README mentions `npm run dev` launching an MCP inspector and tests, but this static review found no actual CI workflow files or committed test suites as verifiable evidence, so per the static calibration rule the score cannot exceed 12. Given the lack of verifiable evidence for tool behavior or error handling, this is scored 8, reflecting a plausible happy path with thin evidence for edge cases and error handling.
Security and permissions 12/20
The server by default sends query data to Mozilla's remote endpoint (mcp.mdn.mozilla.net) and retains interaction data per the linked privacy notice; this is disclosed clearly in the README along with an `X-Moz-1st-Party-Data-Opt-Out` header for opting out — good transparency practice and not a red-line issue (no malware, credential theft, or unconfirmed irreversible actions). However, the documentation does not specify the permission scope of exposed tools, whether any high-risk operations require confirmation, or detailed data-flow differences between local and remote modes, placing it in the 'main risks visible but permission scoping/confirmation incomplete' band rather than full marks.
Maintenance 10/20
The repository is not archived, uses the MPL-2.0 open-source license, and shows some activity signals (182 stars, only 5 open issues). However, no commit history, release cadence, dependency-update policy, or security-response channel is evidenced in the available material, so maintenance governance maturity cannot be confirmed, placing it in the 'active but governance/versioning gaps' range.
Documentation 11/20
The README covers both remote and local setup, links to a privacy notice, explains how to opt out of data collection, and references an acceptable use policy — adequate for basic install and compliance awareness. However, there is no documentation of tool parameters, response formats, rate limits, cost, or troubleshooting, and no manifest was available to cross-check, leaving clear documentation gaps that prevent a top score.
Setup experience 12/20
Remote setup requires only a single `claude mcp add` command, and local setup needs just `npm install` and `npm start`, which is straightforward and reasonably cross-platform via Node.js. However, this static review found no real CI workflow or committed tests covering the server's key paths as execution evidence, so per calibration the score cannot exceed 15; the lack of varied client configuration examples or troubleshooting guidance further caps the score at 12.

Static review · not runListed 2026-08-26

Read the FMRS scoring method →

Fit and risk

What it can accessUses the network

Best for

  • Web developers who need accurate, current web platform documentation
  • Coding agents aiming to reduce inaccuracies caused by outdated LLM training data

Not for

  • Users who require strict data-privacy guarantees and want no query logging whatsoever
  • Production workflows requiring a stable, guaranteed-uptime API, since this server is experimental and may be withdrawn at any time

Required permissions

  • The server itself does not require access to local files or a codebase
  • Using the remote server sends query content to Mozilla's servers

Risks and side effects

  • The README states that query data is stored for analytics; it is not linked to identifying user information, but private details a user shares with the LLM could inadvertently be included in logged queries
  • As an experimental project, the server may be withdrawn at any time, making it unsuitable for dependencies requiring long-term stability
  • Use of the remote server requires compliance with Mozilla's Acceptable Use Policy

Setup

Before you start

Runtime：Node.js · Hosted (no local runtime)

Remote: add Mozilla's hosted remote server to your tool, e.g. in Claude Code run claude mcp add --transport http mdn https://mcp.mdn.mozilla.net/. Local: run npm install to install dependencies, then npm start to launch the server, and add the local endpoint, e.g. claude mcp add --transport http mdn-local http://localhost:3002/. For local development, npm run dev starts the dev server, MCP inspector, and tests together.

Check that it works

Add the server with `claude mcp add --transport http mdn https://mcp.mdn.mozilla.net/`, then ask the client an MDN documentation question (e.g. browser compatibility for a CSS property); an accurate MDN-backed answer confirms the connection.

Troubleshooting

  1. Send the `X-Moz-1st-Party-Data-Opt-Out: 1` header to opt out of first-party analytics
  2. For local runs, confirm `npm install` completed and the default port (3002) is free
  3. Verify the client is configured with http transport and the correct endpoint (remote or local URL)

Things to try

Once connected, you can ask your AI assistant things like:

  • Search MDN for documentation on Array.prototype.at
  • Look up browser compatibility data for the flexbox properties
  • Find the latest MDN docs for the CSS :has() selector

Use cases

Querying MDN documentation for Web APIs, HTML/CSS/JS from within a coding assistant
Checking browser compatibility data for a given web feature
Letting a coding agent verify whether a platform feature is still valid or deprecated before generating code

Supported clients

Claude Code

Listed from the project's documentation, not tested by this site.

Overview

The MDN MCP server is an experimental server maintained by Mozilla's MDN team that exposes MDN's search, documentation, and browser compatibility data to LLMs and coding agents. The goal is to give these tools a reliable, up-to-date source of web platform documentation instead of relying on potentially outdated training data. The repository lives at mdn/mcp under the MPL-2.0 license; the README does not list specific tool names or parameters, so the exact tool set cannot be confirmed from the available source.

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Source revision 284bc79e6a44 Data synced 2026-10-12 Read the FMRS scoring method