ClaudeForSafari

Claude for Safari

Gives Claude Desktop the ability to control Safari — navigate pages, read content, click elements, fill forms — via the MCP protocol, just like "Claude in Chrome".

Architecture

Claude Desktop  (MCP stdio)
      ↕  JSON-RPC
  bridge/bridge.js  (Node.js)
      ↕  WebSocket  ws://localhost:45678
Safari Extension background.js  (MV2)
      ↕  browser.tabs / executeScript
    Active Safari tab

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Repository structure

claudeForSafari/                  ← git root
├── .gitignore
├── README.md
├── bridge/                       ← Node.js bridge (MCP ↔ WebSocket)
│   ├── bridge.js
│   ├── package.json
│   └── package-lock.json
└── app/                          ← Xcode project
    ├── claudeExtension.xcodeproj
    ├── claudeExtension/          ← Swift host app (macOS)
    └── claudeExtension Extension/
        └── Resources/            ← SINGLE SOURCE for extension files
            ├── manifest.json
            ├── background.js
            ├── content.js
            ├── popup.html / popup.js / popup.css
            ├── images/
            └── _locales/

Rule: all extension file edits go directly in app/claudeExtension Extension/Resources/. There is no separate safari-extension/ folder.

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Requirements

• macOS 14+ (Sonoma or later)
• Xcode 16+
• Node.js v18+ — nodejs.org if not yet installed
• An Apple developer account (free account is enough for local use)
• Claude Desktop with MCP support

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Installation

Step 1 — Clone the repository

git clone git@github.com:Lyosis/claudeForSafari.git
cd claudeForSafari

Step 2 — Install bridge dependencies

cd bridge
npm install
cd ..

Step 3 — Build the extension in Xcode

1. Open app/claudeExtension.xcodeproj in Xcode
2. Select the claudeExtension scheme (the host app)
3. Choose My Mac as the destination
4. Press Cmd+R — Xcode builds and launches the app

macOS will show a banner: "claudeExtension wants to add a Safari extension" → click Open Safari Preferences and enable the extension.

Step 4 — Enable the extension in Safari

1. Safari → Settings (Cmd+,) → Extensions tab
2. Check claudeExtension
3. In the right column → Allow on all websites

Without this permission, script injection into pages will fail silently.

Step 5 — Configure Claude Desktop

Open (or create):

~/Library/Application Support/Claude/claude_desktop_config.json

Add the safari entry under mcpServers:

{
  "mcpServers": {
    "safari": {
      "command": "node",
      "args": [
        "/absolute/path/to/claudeForSafari/bridge/bridge.js"
      ]
    }
  }
}

Replace /absolute/path/to/ with the actual path where you cloned the repo.

If node is not in Claude Desktop's PATH, use its full path:

which node   # e.g. /usr/local/bin/node or /opt/homebrew/bin/node

Then restart Claude Desktop.

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Usage

The bridge starts automatically with Claude Desktop.
Safari must be open with the extension enabled.

The extension reconnects automatically to the bridge after sleep or after visiting Safari Settings — no manual action required.

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Available tools (13)

safari_form_input supports <input> and <textarea> fields. Rich text editors using contenteditable (Notion, Gmail compose, etc.) are not yet supported.

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Troubleshooting

"Safari extension not connected"

• Is Safari open? Is the extension checked in Safari → Extensions?
• Check the bridge is running: ps aux | grep bridge.js
• Check logs: Console.app → filter by claude-safari

Permission denied on script injection
→ Safari → Settings → Extensions → claudeExtension → Allow on all websites

safari_get_page_text fails on an internal tab
→ Internal Safari pages (favorites://, about:blank, etc.) cannot be injected. Navigate to an http:// or https:// URL first.

Bridge won't start
→ Check Node.js: node -v (v18+ required)
→ Use the absolute path to node in claude_desktop_config.json

Xcode — "No signing certificate"
→ Xcode → Settings → Accounts → add your Apple ID → Download Manual Profiles

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Security model

The bridge listens on ws://localhost:45678 — localhost only, never exposed to the network.

However, any local process can connect to that port. There is no cryptographic authentication between the bridge and the Safari extension. The threat model assumes that other processes running under your user account are trusted. If you run untrusted local software, be aware that it could theoretically connect to the bridge.

safari_javascript executes arbitrary JavaScript in the active tab by design. Treat it like browser DevTools — only use it on pages you trust.

Development

All extension file edits go in:

app/claudeExtension Extension/Resources/

After editing background.js or manifest.json:

1. Rebuild in Xcode (Cmd+R)
2. Safari → Settings → Extensions → disable then re-enable the extension
   (or restart Safari)

The bridge (bridge/bridge.js) does not need a rebuild — Node.js picks up changes on the next Claude Desktop restart.

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License

MIT