OmniScrape MCP

A free, open-source point-and-click web scraper that plugs your browser straight into Claude over the Model Context Protocol.

Highlight elements on any page with your mouse, and Claude can read exactly what you picked — or the whole page as clean Markdown — without you copying, pasting, or handing an API key to a scraping service.

Pick one price in a list and OmniScrape finds the other 47.

How it fits together

An MCP server is a local Node process. The scraping has to happen inside a real browser, in a real page's DOM. Those two worlds cannot see each other, so the extension dials into a loopback WebSocket the server owns:

┌──────────┐   stdio    ┌──────────────────┐   ws://127.0.0.1:3000   ┌───────────────────┐
│  Claude  │◄──────────►│  MCP server      │◄───────────────────────►│ Chrome extension  │
│          │  JSON-RPC  │  (Node)          │      request/response   │  (Manifest V3)    │
└──────────┘            └──────────────────┘                         └─────────┬─────────┘
                                                                               │ scripting
                                                                     ┌─────────▼─────────┐
                                                                     │  the page's DOM   │
                                                                     └───────────────────┘

Data flows two ways:

• Pull — Claude calls a tool, the server asks the extension, the extension scrapes and answers. Exposed as MCP tools.

• Push — you click Send to Claude. There is no tool call in flight to attach that to, so captures land in a server-side inbox exposed as MCP resources, and the server fires resources/list_changed.

Related MCP server: wasp-mcp

Install

Requires Node 20+ and Chrome 114+.

git clone <this-repo> && cd omniscrape-mcp
npm run install:all

Register the server with Claude Code:

claude mcp add omniscrape -- node "$(pwd)/mcp-server/src/index.js"

{
  "mcpServers": {
    "omniscrape": {
      "command": "node",
      "args": ["<absolute-path>/mcp-server/src/index.js"]
    }
  }
}

Then load the extension — there is no build step:

1. chrome://extensions → enable Developer mode

2. Load unpacked → pick the extension/ folder

3. Click the OmniScrape icon, then Grant page access

The status dot goes green when the panel reaches the server. Claude launches the server itself, so start Claude first (or run npm start in mcp-server to test standalone).

Using it

Say things like:

• "Read the page I'm looking at and summarise the argument."

• "Scrape what I selected and put it in a table."

• "Pull every product name and price off this page."

Or drive it from the panel: Start Selecting Elements → click things → Send to Claude.

Selection mode swallows page clicks, so picking a product title does not navigate away. Hovering shows how many similar elements exist; clicking one row of a list captures the whole column. Each pick becomes a field you can rename, scope to All or One, or drop. Esc exits.

Tools

Plus resources at omniscrape://captures for anything pushed with the button.

Full options in mcp-server/README.md.

Repository layout

mcp-server/    Node MCP server + WebSocket bridge
extension/     Manifest V3 Chrome extension (no build step)
tests/         Extension tests: engine, bridge integration, package integrity

Tests

npm test

71 tests, none of them mocking the thing under test:

• Server (17) — spawns the real server, speaks real MCP JSON-RPC over its stdio, connects a fake extension over the real WebSocket. Covers the handshake, tool schemas and defaults, origin rejection, mid-flight disconnects, malformed frames, and pushed captures.

• Selection engine (26) — loads the real content script and the real vendored libraries into a jsdom page and drives it through the same message interface the service worker uses. Covers selector generalisation, state-class filtering, click suppression, Markdown/table/link conversion, truncation, and that Readability never touches the live DOM.

• Bridge integration (11) — imports the shipped WebSocket client unchanged, points it at a spawned server, and drives that same process over stdio, so a tool call travels the whole path. Includes killing the server mid-session and asserting the client reconnects on its own and still works.

• Package integrity (11) — every file the manifest references exists, no inline scripts the extension CSP would block, vendored libraries expose their globals and are not ESM, and the two copies of the wire protocol match.

Security posture

The bridge serves the contents of whatever page you are looking at, so it is deliberately narrow:

• Loopback only. Bound to 127.0.0.1, never the network.

• Origin allowlist. A WebSocket is exempt from CORS, so any page you visit can open a socket to ws://127.0.0.1:3000. It cannot forge its Origin header, so requiring chrome-extension:// is what stops a malicious tab from connecting and reading your scrapes. Two tests cover this.

• Optional token. The origin check does not prove which extension is connecting, and any local process running as you could present a plausible origin. Set OMNISCRAPE_TOKEN if that matters to you.

• Nothing on disk. Captures live in memory for the process lifetime.

• Page access is opt-in, requested from a button rather than demanded at install.

See Locking down the bridge.

Known limits

• Top frame only. Content inside iframes is not scraped.

• Selectors are structural. A page that re-renders with different markup invalidates them; the panel shows 0× when that happens.

• Readability is all or nothing. Turn it off for dashboards, search results, and tables — it discards exactly that kind of content.

• One browser at a time. With several profiles connected, requests go to the most recently active one.

License

MIT. Vendored libraries keep their own licenses — see extension/vendor/.