browser-ctl 0.1.1

Control your browser from the command line via a Chrome extension + WebSocket bridge

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browser-ctl

Browser automation built for AI agents.
Give your LLM a real Chrome browser — with your sessions, cookies, and extensions — through simple CLI commands.

pip install browser-ctl

bctl go https://github.com
bctl click "a.search-button"
bctl type "input[name=q]" "browser-ctl"
bctl press Enter
bctl screenshot results.png

The Problem with Existing Browser Automation

Tools like browser-use, Playwright MCP, and Puppeteer are powerful, but they share a set of pain points when used with AI agents:

Pain point	Typical tools	browser-ctl
Heavy browser binaries — must download and manage a bundled Chromium (~400 MB)	Playwright, Puppeteer	Uses your existing Chrome — zero browser downloads
No access to real sessions — launches a fresh, empty browser with no cookies, logins, or extensions	browser-use, Playwright MCP	Controls your real Chrome — all sessions, cookies, and extensions intact
Anti-bot detection — headless browsers are flagged and blocked by many websites	Puppeteer, Playwright	Uses your real browser profile — indistinguishable from normal browsing
Complex SDK integration — requires importing libraries and writing async code	browser-use, Stagehand	Pure CLI with JSON output — any LLM can call bctl click "button"
Heavy dependencies — Playwright alone pulls ~50 MB of packages + browser binary	Playwright, Puppeteer	CLI is stdlib-only; server needs only aiohttp
Token-inefficient for LLMs — verbose API calls waste context window tokens	SDK-based tools	Concise commands: bctl text h1 vs pages of boilerplate

Designed for LLM Agents

browser-ctl is purpose-built for AI agent workflows:

• Tool-calling ready — every command is a single shell call returning structured JSON, perfect for function-calling / tool-use patterns
• Built-in AI skill — ships with SKILL.md that teaches AI agents (Cursor, OpenCode, etc.) the full command set and best practices
• Real browser = real access — your LLM can operate on authenticated pages (Gmail, Jira, internal tools) without credential management
• Deterministic output — JSON responses with CSS-selector-based queries, no vision model needed for most tasks
• Minimal token cost — bctl select "a.link" -l 5 returns structured data in one call vs multi-step screenshot → vision → parse loops

# Install the AI skill for Cursor IDE in one command
bctl setup cursor

How It Works

AI Agent / Terminal  ──HTTP──▶  Bridge Server  ◀──WebSocket──  Chrome Extension
     (bctl CLI)                  (:19876)                      (your browser)

1. CLI (bctl) sends commands via HTTP to a local bridge server
2. Bridge server relays them over WebSocket to the Chrome extension
3. Extension executes commands using Chrome APIs & content scripts in your real browser
4. Results flow back the same path as JSON

The bridge server auto-starts on first command — no manual setup needed.

Installation

Step 1 — Install the Python package:

pip install browser-ctl

Step 2 — Load the Chrome extension:

bctl setup

Then in Chrome: chrome://extensions → Enable Developer mode → Load unpacked → select ~/.browser-ctl/extension/

Step 3 — Verify:

bctl ping
# {"success": true, "data": {"server": true, "extension": true}}

Command Reference

Navigation

Command	Description
bctl navigate <url>	Navigate to URL   (aliases: nav, go; auto-prepends https://)
bctl back	Go back in history
bctl forward	Go forward   (alias: fwd)
bctl reload	Reload current page

Interaction

Command	Description
bctl click <sel> [-i N]	Click element (CSS selector, optional Nth match)
bctl hover <sel> [-i N]	Hover over element
bctl type <sel> <text>	Type text into input/textarea
bctl press <key>	Press key — Enter submits forms, Escape closes dialogs
bctl scroll <dir|sel> [px]	Scroll: up / down / top / bottom or element into view
bctl select-option <sel> <val>	Select dropdown option   (alias: sopt) [--text]
bctl drag <src> [target]	Drag to element or offset [--dx N --dy N]

DOM Query

Command	Description
bctl text [sel]	Get text content (default: body)
bctl html [sel]	Get innerHTML
bctl attr <sel> [name] [-i N]	Get attribute(s) of element
bctl select <sel> [-l N]	List matching elements   (alias: sel)
bctl count <sel>	Count matching elements
bctl status	Current page URL and title

JavaScript

Command	Description
bctl eval <code>	Execute JS in page context (auto-bypasses CSP)

Tabs

Command	Description
bctl tabs	List all tabs
bctl tab <id>	Switch to tab by ID
bctl new-tab [url]	Open new tab
bctl close-tab [id]	Close tab (default: active)

Screenshot & Files

Command	Description
bctl screenshot [path]	Capture screenshot   (alias: ss)
bctl download <target> [-o path] [-i N]	Download file/image   (alias: dl; -o supports absolute paths)
bctl upload <sel> <files...>	Upload file(s) to <input type="file">

Wait & Dialog

Command	Description
bctl wait <sel|seconds> [timeout]	Wait for element or sleep
bctl dialog [accept|dismiss] [--text val]	Handle next alert / confirm / prompt

Server

Command	Description
bctl ping	Check server & extension status
bctl serve	Start server in foreground
bctl stop	Stop server

Examples

Search and extract

bctl go "https://news.ycombinator.com"
bctl select "a.titlelink" -l 5       # Top 5 links with text, href, etc.

Fill a form

bctl type "input[name=email]" "[e-mail]"
bctl type "input[name=password]" "hunter2"
bctl select-option "select#country" "US"
bctl upload "input[type=file]" ./resume.pdf
bctl click "button[type=submit]"

Scroll and screenshot

bctl go "https://en.wikipedia.org/wiki/Web_browser"
bctl scroll down 1000
bctl ss page.png

Handle dialogs

bctl dialog accept              # Set up handler BEFORE triggering
bctl click "#delete-button"     # This triggers a confirm() dialog

Drag and drop

bctl drag ".task-card" ".done-column"
bctl drag ".range-slider" --dx 50 --dy 0

Shell scripting

# Extract all image URLs from a page
bctl go "https://example.com"
bctl eval "JSON.stringify(Array.from(document.images).map(i=>i.src))"

# Wait for SPA content to load
bctl go "https://app.example.com/dashboard"
bctl wait ".dashboard-loaded" 15
bctl text ".metric-value"

Output Format

All commands return JSON to stdout:

// Success
{"success": true, "data": {"url": "https://example.com", "title": "Example"}}

// Error
{"success": false, "error": "Element not found: .missing"}

Non-zero exit code on errors — works naturally with set -e and && chains.

Architecture

┌─────────────────────────────────────────────────────┐
│  AI Agent / Terminal                                │
│  $ bctl click "button.submit"                       │
│       │                                             │
│       ▼  HTTP POST localhost:19876/command           │
│  ┌──────────────────────┐                           │
│  │   Bridge Server      │  (Python, aiohttp)        │
│  │   :19876             │                           │
│  └──────────┬───────────┘                           │
│             │  WebSocket                            │
│             ▼                                       │
│  ┌──────────────────────┐                           │
│  │  Chrome Extension    │  (Manifest V3)            │
│  │  Service Worker      │                           │
│  └──────────┬───────────┘                           │
│             │  chrome.scripting / chrome.debugger    │
│             ▼                                       │
│  ┌──────────────────────┐                           │
│  │  Your Real Browser   │  (sessions, cookies, etc) │
│  └──────────────────────┘                           │
└─────────────────────────────────────────────────────┘

Component	Details
CLI	Stdlib only, communicates via HTTP
Bridge Server	Async relay (aiohttp), auto-daemonizes
Extension	MV3 service worker, auto-reconnects via chrome.alarms
Eval	Dual strategy: MAIN-world injection (fast) + CDP fallback (CSP-safe)

Requirements

• Python >= 3.11
• Chrome / Chromium with the extension loaded
• macOS, Linux, or Windows

Privacy

All communication is local (127.0.0.1). No analytics, no telemetry, no external servers. See PRIVACY.md.

License

MIT