Show HN: Browserr – An MCP-first browser for AI agents (one Rust binary)

A developer released Browserr, an MCP-first browser for AI agents shipped as a single ~120 MB Rust binary with zero dependencies, exposing 42 Model Context Protocol tools over JSON on a loopback socket and zero Chrome DevTools Protocol endpoints. Browserr is built on the Servo engine and emphasizes fail-closed behavior: unauthenticated sockets receive nothing, intercepted requests unanswered after 5 seconds are denied, and missing credentials fail closed, with an append-only action log, network evidence ring buffer and a confirm gate on payment submits. The project also ships a dependency-free Python driver.py and claims React 18 and Vue 3 compatibility, positioning alternative engines against Chromium wrappers as its edge.

Scope 01 / 05 Everything an agent needs. Built agent-first: extraction over pixels, stable refs over coordinates, failures you can catch instead of hangs. Three commitments shape the whole engine: it blocks when unsure, it hands the page to a human when a human is needed, and it leaves evidence for everything it did. | Command | Covers | |---|---| | read | Structured page reads. Prose via read page , or read structure : every element with its rect and selector; fields carry label, constraints, state and validity. | | act | Selector interaction. click element and set value — real pointer events, React/Vue-safe writes. | | wait | SPA-aware timing. Wait for selectors and readiness — no sleeps, no flaky scripts. | | observe | Console capture. Page messages and network errors arrive as events. | | files | Downloads. Fetched straight to disk, without page cookies. | | survive | Fast failure, not hangs. A dead engine surfaces instantly; ephemeral profiles give every run a clean slate. | | block | Adblock built in. EasyList-based, refreshed weekly. | | gpu | Rendering. CPU by default — starts anywhere; --gpu opts into hardware. Screenshots on demand, per tab. | | compat | SPA-ready. React 18 and Vue 3 render and react; IntersectionObserver, IndexedDB, Web Animations, WebGL and WebGL2 via ANGLE, no GPU needed , clipboard, DecompressionStream; requestIdleCallback and crypto.subtle digests via built-in shims where Servo omits them. | | secure | Token-gated attach. Unauthenticated sockets get nothing — not even events. | | intercept | Fail-closed interception. Requests held for an allow / deny / respond decision; unanswered means denied after 5 s. | | auth | Challenges surfaced, not swallowed. Auth and file-picker events; missing credentials fail closed. | | evidence | Net evidence. Every fetch/XHR recorded in a ring buffer, in every frame. | | frames | Frame tree. List frames and walk same-origin ones; cross-origin frames report their url only. | | fill | Form filling. A whole form in one round trip, with type-aware writes. | | submit | Submit and read the outcome. Runs the page's validation, then reports url, alerts and invalid fields. | | point | Shared references. Stable refs and numbered screenshot boxes: the agent says "click 7" and the human knows which one that is. | | proxy | Upstream proxy routing. browser start proxy=... routes all http/https traffic through a CONNECT tunnel basic auth in the URL, per-engine rotation ; document status reports the main document's real HTTP status so a block serving a fake 404 is distinguishable from a dead page. | | handoff | Humans take over in a real native window. Start MCP with headed:true; direct mouse and keyboard input keep working while agent mutations are paused. CAPTCHA support still depends on Servo compatibility. | | trust | Fail-closed by design. Persistent profiles, evidence shots, an append-only action log, a credential store and a confirm gate on payment submits. | Protocol 02 / 05 The entire protocol, in full. JSON over loopback. One client, no hidden state — the opposite of CDP's 1000+ endpoints. Events: - Commands - 22 - MCP tools - 42 - Binary - ~120 MB - CDP endpoints - 0 - Dependencies - 0 SDK 03 / 05 Three ways in. Same engine underneath; pick the integration you already have. | Surface | Covers | |---|---| | mcp | Model Context Protocol server with 42 tools, stdlib only. Any MCP-capable agent — Claude, Kai, your own — drives Browserr with zero integration code. | | python | driver.py wraps the raw protocol: navigation, extraction, form filling, screenshots. No dependencies. | | raw | Anything that can write JSON lines to a socket. Bindings in any language are an afternoon. | Position 04 / 05 Where it sits in 2026. Chromium wrappers are the default; alternative engines are the bet. Browserr's edge is the local, trust-first, human-in-the-loop. | | Browserr | Lightpanda | Obscura | Chromium headless | |---|---|---|---|---| | engine | Servo | own Zig | own Rust | Blink | | js engine | SpiderMonkey | own | own | V8 | | mcp-native | yes, 42 tools | no | partial | via wrappers | | protocol size | 22 commands | CDP-compatible | own + CDP | 1000+ endpoints | | footprint | one ~120 MB binary | ~16× less than Chromium | ~30 MB | ~200 MB+ | | web compat | Servo 0.8 text, docs, forms, SPAs | growing | growing | full | | human handoff | native window, pause, wait for user | headless only | headless only | via wrappers | | trust layer | evidence, action log, confirm gate | no | no | no | | network policy | fail-closed, held to a decision | CDP opt-in | CDP opt-in | CDP opt-in | Install 05 / 05 Get Browserr in seconds. One package per platform: the engine binary, Python SDK, and the MCP server. Windows x64 Download the zip, unpack anywhere, and point your agent at the MCP server. CPU rendering works out of the box; pass --gpu for hardware rendering. ↓ Download for Windows https://github.com/Omodaka9375/browserr/releases/latest Linux x64 / ARM64 Download the tarball, unpack anywhere, and point your agent at the MCP server. Works headless without a GPU; ARM64 covers the Raspberry Pi 4/5. macOS Apple Silicon Download the tarball, unpack anywhere, and point your agent at the MCP server. Works headless out of the box. ↓ Download for macOS https://github.com/Omodaka9375/browserr/releases/latest Start Start driving the web with your agents. Free, open source, no account, no telemetry. Runs on every machine.