Chrome Extension

The victauri-browser crate provides MCP access to any website running in Chrome, Edge, Brave, or Arc — not just Tauri applications.

What It Does

The Chrome extension + native messaging host extends Victauri’s inspection capabilities to regular web pages. An AI agent can connect via MCP on localhost:7474 and get DOM snapshots, interact with elements, evaluate JavaScript, inspect styles, and more — all on arbitrary websites.

This is useful for:

Web scraping with semantic understanding
Cross-site testing workflows
Automating web tasks that span both Tauri apps and web services
General browser automation via MCP

Installation

1. Install the Native Host Binary

cargo install victauri-browser

Or build from source:

cargo build -p victauri-browser --release

2. Register the Native Messaging Host

victauri-browser install

This registers the native messaging host manifest with your browser (Chrome, Edge, Brave, or Arc are auto-detected). The manifest tells the browser how to launch the native host when the extension requests it.

To uninstall:

victauri-browser uninstall

3. Load the Chrome Extension

Open your browser’s extension management page (chrome://extensions)
Enable “Developer mode”
Click “Load unpacked” and select the extensions/chrome/ directory from the Victauri repo

4. Connect via MCP

The native host starts an HTTP server on localhost:7474 (with fallback to 7475-7484 if the port is busy).

{
  "mcpServers": {
    "victauri-browser": {
      "url": "http://127.0.0.1:7474/mcp"
    }
  }
}

Architecture

The communication flow:

MCP Client (Claude Code)
    │
    │ HTTP (localhost:7474)
    ▼
Native Host Binary (victauri-browser)
    │
    │ Chrome Native Messaging (stdio)
    │ 32-bit LE length prefix + UTF-8 JSON
    ▼
Extension Service Worker (MV3)
    │
    │ chrome.tabs.sendMessage()
    ▼
Content Script (ISOLATED world)
    │
    │ CustomEvent (__victauri_command / __victauri_response)
    ▼
JS Bridge (MAIN world)
    │
    │ Direct DOM access
    ▼
Web Page

Components

Native Host Binary (victauri-browser)

Dual role: HTTP server for MCP clients AND native messaging host for Chrome
axum router serves /mcp (MCP protocol), /api/tools (REST), /health, /info
Reads/writes Chrome native messaging format on stdio
BridgeDispatch sends UUID-tagged commands and resolves responses via oneshot channels

Service Worker (MV3 background script)

Manages native messaging connection lifecycle
Routes commands to the correct tab’s content script
Handles tab lifecycle (creation, removal, navigation)
Manages CDP sessions for advanced features

Content Script (ISOLATED world)

Relay between service worker and MAIN world bridge
Uses CustomEvent pattern to cross the world boundary
Injected into all pages matching the extension’s permissions

JS Bridge (MAIN world, 1700+ lines)

Full DOM inspection, interactions, accessibility, performance
Same Playwright-grade actionability checks as the Tauri plugin bridge
CSS inspection, recording, element finding, scroll, hover, click

Available Tools (20)

Tool	Description
`get_plugin_info`	Extension version and status (handled locally)
`tabs.list`	List open browser tabs (handled locally)
`dom_snapshot`	Full accessible DOM tree of active tab
`find_elements`	Search by CSS selector, text, or role
`eval_js`	Evaluate JavaScript in page context
`click`	Click an element by ref
`fill`	Set input value
`type_text`	Type characters one-by-one
`press_key`	Dispatch keyboard event
`hover`	Hover over element
`scroll_into_view`	Scroll element into viewport
`get_styles`	Computed CSS for an element
`get_bounding_boxes`	Element dimensions and box model
`highlight_element`	Draw debug overlay
`clear_highlights`	Remove all overlays
`screenshot`	Capture visible tab as PNG
`navigate`	Go to URL
`get_cookies`	Get cookies for current domain
`get_console_logs`	Captured console entries
`get_network_log`	Fetch/XHR request history

Authentication

The native host supports Bearer token authentication:

# Set via environment variable
VICTAURI_AUTH_TOKEN=my-token victauri-browser serve

Security features:

Constant-time token comparison
Token-bucket rate limiter
Security headers on all responses
Origin guard (blocks non-localhost origins)

Port Behavior

Default port: 7474. If busy, tries 7475 through 7484. The victauri-browser serve command prints the actual port on startup.

Tab Management

The extension tracks tab state (URL, title, bridge readiness). Commands are sent to the active tab by default, or you can target a specific tab by ID using the tab_id parameter where supported.

Special behaviors:

Navigation uses chrome.tabs.update() (not content script window.location) for reliability
Cookies use chrome.cookies.getAll() for httpOnly access
Screenshots use Chrome’s chrome.tabs.captureVisibleTab() API

Keyboard shortcuts

Victauri Documentation