μBrowser
The fastest, cheapest browser automation for Claude.
μBrowser ██████ 51s $0.18
Dev Browser ████████████████████████████████████████ 3m 53s $0.88
Playwright ████████████████████████████████████████████████ 4m 31s $1.45
Benchmarks
Tested on dev-browser-eval game-tracker task with Claude Opus 4.5 (benchmark setup cloned from SawyerHood, eval tasks created independently):
| Method | Time | Cost | Turns |
|---|
| μBrowser | 51s | $0.18 | 7 |
| Dev Browser | 3m 53s | $0.88 | 29 |
| Playwright MCP | 4m 31s | $1.45 | 51 |
Results:
- 5× faster than Dev Browser
- 5× cheaper than Dev Browser
- 8× cheaper than Playwright MCP
Latest local run (dev-browser-eval simulation, HN proxy):
| Method | Time | Cost | Turns | Tokens |
|---|
| Traditional (6 calls) | 17.36s | $0.1439 | 6 | 2177 |
| μBrowser (batch) | 6.87s | $0.0052 | 1 | 204 |
How It Works
1. Batch Execution
Combine 25+ browser actions into a single API call:
{"steps": [
{"tool": "navigate", "args": {"url": "/login"}},
{"tool": "type", "args": {"selector": "#email", "text": "user@test.com"}},
{"tool": "type", "args": {"selector": "#pass", "text": "secret"}},
{"tool": "click", "args": {"selector": "button[type=submit]"}}
], "snapshot": {"when": "final", "maxElements": 40}}
Others make 4 separate calls. We make 1. 75% fewer API calls.
2. Ultra-Compact Snapshot Format
Standard HTML (~180 tokens):
<button id="e1" role="button">Submit</button>
<input id="e2" type="email" placeholder="Email" required>
<input id="e3" type="password" placeholder="Password">
μBrowser (~50 tokens):
btn#e1"Submit"
inp#e2@e~"Email"!r
inp#e3@p~"Password"
70% smaller snapshots. Output tokens cost 5× more than input.
3. Minimal Responses
{"ok":true}
{"ok":true,"snap":"btn#e1\"Submit\"\ninp#e2@e~\"Email\""}
Only return DOM when explicitly requested.
Speed + Cost Tuning
Environment variables:
UBROWSER_BLOCK_STYLESHEETS=1 blocks CSS for faster loads (may affect layout-dependent pages).UBROWSER_MAX_ELEMENTS=40 caps snapshots by default when maxElements is not provided.UBROWSER_PROFILE_DIR=~/.ubrowser/profile browser profile directory for session persistence.UBROWSER_CONSOLE_LIMIT=100 max console messages to retain in buffer.UBROWSER_NETWORK_LIMIT=100 max network requests to retain in buffer.
Snapshot options (per-call overrides):
snapshot.maxElements limits returned elements for browser_snapshot, per-tool snapshots, and browser_batch.
Session Persistence
Browser state (cookies, localStorage, IndexedDB) persists to disk between MCP server restarts. This enables:
- Staying logged in across sessions
- Preserving form data and preferences
- Maintaining shopping carts and app state
Profile stored at ~/.ubrowser/profile by default (customize with UBROWSER_PROFILE_DIR).
Implementation Details
Pre-injected extraction script — Script is injected once and JIT-cached in browser, eliminating recompilation overhead. Subsequent snapshots complete in <1ms.
Batched visibility checks — All getBoundingClientRect() calls happen in a single pass, avoiding layout thrashing that occurs with per-element checks.
MutationObserver caching — DOM changes are tracked via MutationObserver. If nothing changed, cached snapshot returns instantly (0.5ms vs 50ms).
CDP fast operations — Click and type use Chrome DevTools Protocol directly when element positions are known, bypassing Playwright's actionability checks.
Resource blocking — Images, fonts, media blocked at network level via Playwright route interception. Stylesheets preserved for layout accuracy.
Parallel snapshot — Promise.all fetches URL, title, and DOM elements concurrently during batch finalization.
Single-op type — Uses fill() for instant text input when no delay/enter needed, bypassing character-by-character simulation.
Install
Claude Code Plugin (Recommended)
/plugin marketplace add lulzx/claude-code
/plugin install ubrowser@claude-code
Restart Claude Code and the ubrowser MCP tools are ready.
Manual Installation
git clone https://github.com/lulzx/ubrowser && cd ubrowser
npm install && npx playwright install chromium && npm run build
claude mcp add ubrowser -- node "$PWD/build/index.js"
Tools