browser-compat-mcp-server

Browser compatibility and Baseline status for any web feature — offline, from bundled MDN data.

CommunityOnlineNo sign-inGlobalFreeRead-only

What it can do

    What data it sees

    Do you need an account

    No: the server works without sign-in

    Browser compatibility and Baseline status for any web feature — offline, from bundled MDN data.

    How to connect

    How to connect browser-compat-mcp-server to Claude

    The server address to paste into Claude settings:

    https://browser-compat.caseyjhand.com/mcp

    1. Open Claude (claude.ai or the desktop app).
    2. Go to Settings → Connectors.
    3. Click Add custom connector.
    4. Paste the server address copied below into Remote MCP server URL and click Add.
    5. In a chat, click + → Connectors and switch the new connector on.

    Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

    Authorization

    After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

    How to connect browser-compat-mcp-server to ChatGPT

    The server address to paste into ChatGPT settings:

    https://browser-compat.caseyjhand.com/mcp

    1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
    2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
    3. Open Settings → Connectors and click Create.
    4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
    5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
    6. In a new chat open + → Apps/Connectors and enable the connector.

    OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

    Authorization

    On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

    How to connect browser-compat-mcp-server to Cursor

    The server address to paste into Cursor settings:

    https://browser-compat.caseyjhand.com/mcp

    Fastest: click Open in Cursor below and confirm the prompt.

    Manually:

    1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
    2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
    3. Save the file. The server appears in the MCP list; authorize it there if asked.

    Authorization

    If the service needs sign-in, an authorize button appears next to the server in the MCP list.

    Server tool list (5)

    Raw names from tools/list. Only developers need these.

    browsercompat_list_referenceEnumerate the reference vocabulary this server uses: BCD namespaces, BCD browser ids, browserslist agent ids and their BCD counterparts, Baseline states, web-features groups, and ECMAScript snapshots. Use it to build valid inputs for the other tools and to see which target browsers can be evaluated.
    browsercompat_get_featureGet the compatibility record for one web feature: Baseline state and the date it crossed, deprecation and standards status, per-browser version added and removed with flags, vendor prefixes and partial-implementation notes — with every other support statement recorded for that browser, such as an earlier prefixed or flagged release, in other_statements — and the MDN and specification links. Accepts a BCD key such as css.selectors.has or a web-features id such as has; the response echoes which one it matched. A web-features id that spans several BCD keys, such as grid, returns web-features’ own feature-level release per Baseline core browser in feature_support and its compat_keys, 100 per page, in place of per-key fields. An unresolved feature returns found: false with guidance rather than an error.
    browsercompat_check_baselineCheck whether web features are safe to ship: Baseline state and the date it crossed, the browser and version that limits support, whether the feature is deprecated or discouraged, and the share of tracked global traffic that requiring it would exclude. Evaluates up to 20 BCD keys or web-features ids per call; up to 100 may be sent, and entries past the 20th come back unevaluated in omitted_features for the next call.
    browsercompat_search_featuresFind web features by plain name or keyword when the canonical key is unknown, across CSS, JavaScript, HTML, Web APIs, SVG, MathML, WebAssembly, and HTTP headers. Returns ranked matches with the BCD key, the web-features id, the Baseline state, a one-line support summary, and which field matched. Feed a result key into browsercompat_get_feature for the full record.
    browsercompat_compare_supportCompute whether a set of web features clears an explicit browserslist target query. Compares up to 20 features per call; up to 100 may be sent, and entries past the 20th come back unevaluated in omitted_features for the next call. Every call evaluates the whole query: each feature gets a verdict, the count of failing targets, those targets grouped into runs of consecutive query targets per browser in failing_ranges, and its own evaluated and unevaluated target counts with the share of tracked traffic each covers. The target rows behind those numbers — which release each target maps to, which targets were not evaluated and why, and the failing and unevaluated targets of each feature, a failing row carrying the prefix, alternative name, or flag behind its verdict — cover at most ten query targets per call; page through them with target_offset and target_limit, and the verdicts, coverage, and totals stay identical on every page. A target counts as evaluated only where compatibility data was read for it, so a feature clears only when every target in the query was evaluated and supports it, and is inconclusive otherwise — a query that includes a browser with no compatibility data, as "defaults" does, never clears. A BCD key is judged on its own per-browser support. A web-features id spanning several keys, such as grid, is judged on the release web-features lists for the feature as a whole in each Baseline core browser, as support_source says; its other browsers are not evaluated.