Lightpanda Browser
The headless browser built from scratch for AI agents and automation.
Not a Chromium fork. Not a WebKit patch. A new browser, written in Zig.
Benchmarks
Requesting 933 real web pages over the network on a AWS EC2 m5.large instance. See benchmark details.
| Metric | Lightpanda | Headless Chrome | Difference |
|---|---|---|---|
| Memory (peak, 100 pages) | 123MB | 2GB | ~16 less |
| Execution time (100 pages) | 5s | 46s | ~9x faster |
Quick start
Install
Package Managers
Latest nightly from Homebrew:
brew install lightpanda-io/browser/lightpandaLatest nightly from Arch Linux User Repository:
yay -S lightpanda-nightly-binDownload from the nightly builds
You can download the last binary from the nightly builds for Linux and MacOS for both x86_64 and aarch64.
For Linux
curl -L -o lightpanda https://github.com/lightpanda-io/browser/releases/download/nightly/lightpanda-x86_64-linux && \
chmod a+x ./lightpandaVerify the binary before running anything:
./lightpanda versionLinux aarch64 is also available
Note: The Linux release binaries are linked against glibc. On musl-based distros (Alpine, etc.) the binary fails with
cannot execute: required file not foundbecause the glibc dynamic linker is missing. Use a glibc-based base image (e.g.,FROM debian:bookworm-slimorFROM ubuntu:24.04) or build from sources.
For MacOS
curl -L -o lightpanda https://github.com/lightpanda-io/browser/releases/download/nightly/lightpanda-aarch64-macos && \
chmod a+x ./lightpandaMacOS x86_64 is also available
For Windows + WSL2
Lightpanda has no native Windows binary. Install it inside WSL following the Linux steps above.
WSL not installed? Run wsl --install from an administrator shell, restart, then open wsl.
See Microsoft's WSL install guide for details.
Your automation client (Puppeteer, Playwright, etc.) can run either inside WSL or on the Windows host. WSL forwards localhost:9222 automatically.
Install from Docker
Lightpanda provides official Docker
images for both Linux amd64 and
arm64 architectures.
The following command fetches the Docker image and starts a new container exposing Lightpanda's CDP server on port 9222.
docker run -d --name lightpanda -p 127.0.0.1:9222:9222 lightpanda/browser:nightlyDump a URL
./lightpanda fetch --obey-robots --dump html --log-format pretty --log-level info https://demo-browser.lightpanda.io/campfire-commerce/You can use --dump markdown to convert directly into markdown.
--wait-until, --wait-ms, --wait-selector and --wait-script are
available to adjust waiting time before dump.
Start a CDP server
./lightpanda serve --obey-robots --log-format pretty --log-level info --host 127.0.0.1 --port 9222Once the CDP server started, you can run a Puppeteer script by configuring the
browserWSEndpoint.
Example Puppeteer script
import puppeteer from 'puppeteer-core';
// use browserWSEndpoint to pass the Lightpanda's CDP server address.
const browser = await puppeteer.connect({
browserWSEndpoint: "ws://127.0.0.1:9222",
});
// The rest of your script remains the same.
const context = await browser.createBrowserContext();
const frame = await context.newPage();
// Dump all the links from the frame.
await frame.goto('https://demo-browser.lightpanda.io/amiibo/', {waitUntil: "networkidle0"});
const links = await frame.evaluate(() => {
return Array.from(document.querySelectorAll('a')).map(row => {
return row.getAttribute('href');
});
});
console.log(links);
await frame.close();
await context.close();
await browser.disconnect();Agent mode
lightpanda agent lets you drive the browser with a native agent. Describe what
you want in plain English or with slash commands, and it controls the browser:
navigating pages, clicking through flows, filling forms, extracting structured
data. Think of it as a robot you're directing to use the web, more than a
chatbot you're having a conversation with.
Because the agent runs inside the same process as the browser, every tool call is a direct operation and you retain Lightpanda's speed and memory advantage.
The output of an agent session is a
PandaScript: vanilla JavaScript
with a small set of native browser primitives built directly into Lightpanda.
Run /save to export one from your current session, then replay it with
lightpanda run <script>.js. Scripts are deterministic and token-free, so
you can prototype with the LLM and ship the output to production without a
model at runtime.
It supports Anthropic, OpenAI, Gemini, Google Vertex AI, Hugging Face, and
local models via Ollama. You can also run without an LLM using --no-llm,
which drops you into the REPL. See the
agent documentation for the full
reference.
./lightpanda agent # auto-detects API key from env
./lightpanda agent --task "top story on news.ycombinator.com?"
./lightpanda agent --no-llm # basic REPL, no LLM
./lightpanda run session.js # run a recorded script
./lightpanda agent --provider gemini --task "..." # force a specific provider
VERTEX_API_KEY=... ./lightpanda agent --provider vertex # Vertex AI, express mode
GOOGLE_CLOUD_PROJECT=my-proj ./lightpanda agent --provider vertex # Vertex AI, token via gcloud authNative MCP and skill
The MCP server communicates via MCP JSON-RPC 2.0 over stdio.
Add to your MCP configuration:
{
"mcpServers": {
"lightpanda": {
"command": "/path/to/lightpanda",
"args": ["mcp"]
}
}
}HTTP transport and independent sessions
For serving several agents from one process, start the MCP server over HTTP
instead of stdio by giving it a port (add --host x.x.x.x to specify the
interface to listen on):
lightpanda mcp --port 9223Clients POST JSON-RPC to http://host:9223/mcp. Each connection is routed to
its own browsing session — its own page, cookies and memory — so agents no
longer clobber each other's page:
- A client that
initializes without anMcp-Session-Idheader is assigned a fresh session; the id comes back in the response'sMcp-Session-Idheader. Send it on subsequent requests to stay on that session (isolation). - Two agents that send the same
Mcp-Session-Idshare one browsing context (sharing — e.g. a workflow where several agents work the same page). - The
session_new,session_listandsession_closetools manage sessions explicitly. SendingDELETE /mcpwith anMcp-Session-Idcloses that session.
A skill is available in lightpanda-io/agent-skill.
Telemetry
By default, Lightpanda collects and sends usage telemetry. This can be disabled by setting an environment variable LIGHTPANDA_DISABLE_TELEMETRY=true. You can read Lightpanda's privacy policy at: https://lightpanda.io/privacy-policy.
Core dumps
Set LIGHTPANDA_DISABLE_CORE_DUMP (to any value) to suppress crash core dumps by zeroing the soft RLIMIT_CORE at startup.
Status
Lightpanda is in Beta and currently a work in progress. Stability and coverage are improving and many websites now work. You may still encounter errors or crashes. Please open an issue with specifics if so.
Here are the key features we have implemented:
- CORS #2015
- HTTP loader (Libcurl)
- HTML parser (html5ever)
- DOM tree
- Javascript support (v8)
- DOM APIs
- Ajax
- XHR API
- Fetch API
- DOM dump
- CDP/websockets server
- Click
- Input form
- Cookies
- Custom HTTP headers
- Proxy support
- Network interception
- Respect
robots.txtwith option--obey-robots
NOTE: There are hundreds of Web APIs. Developing a browser (even just for headless mode) is a huge task. Coverage will increase over time.
Build from sources
Prerequisites
Lightpanda is written with Zig 0.15.2. You have to
install it with the right version in order to build the project.
Lightpanda also depends on v8, Libcurl and html5ever.
To be able to build the v8 engine, you have to install some libs:
For Debian/Ubuntu based Linux:
sudo apt install xz-utils ca-certificates \
pkg-config libglib2.0-dev \
clang make curl git
You also need to install Rust.
For systems with Nix, you can use the devShell:
nix develop
For MacOS, you need cmake and Rust.
brew install cmake
Build and run
You can build the entire browser with make build or make build-dev for debug
env.
But you can directly use the zig command: zig build run.
Embed v8 snapshot
Lighpanda uses v8 snapshot. By default, it is created on startup but you can embed it by using the following commands:
Generate the snapshot.
zig build snapshot_creator -- src/snapshot.bin
Build using the snapshot binary.
zig build -Dsnapshot_path=../../snapshot.bin
See #1279 for more details.
Test
Unit Tests
You can test Lightpanda by running make test.
make test # Run all tests
make test F="server" # Filter by substring
TEST_FILTER="WebApi: #selector_all" make test # Filter main + subtest (separator: #)
TEST_VERBOSE=true make test
TEST_FAIL_FIRST=true make test
METRICS=true make test # Capture allocation/duration metrics as JSONEnd to end tests
To run end to end tests, you need to clone the demo
repository into ../demo dir.
You have to install the demo's node requirements
You also need to install Go > v1.24.
make end2end
Web Platform Tests
Lightpanda is tested against the standardized Web Platform Tests.
We use a fork including a custom
testharnessreport.js.
For reference, you can easily execute a WPT test case with your browser via wpt.live.
Configure WPT HTTP server
To run the test, you must clone the repository, configure the custom hosts and generate the
MANIFEST.json file.
Clone the repository with the fork branch.
git clone -b fork --depth=1 git@github.com:lightpanda-io/wpt.git
Enter into the wpt/ dir.
Install custom domains in your /etc/hosts
./wpt make-hosts-file | sudo tee -a /etc/hosts
Generate MANIFEST.json
./wpt manifest
Use the WPT's setup guide for details.
Run WPT test suite
An external Go runner is provided by
github.com/lightpanda-io/demo/
repository, located into wptrunner/ dir.
You need to clone the project first.
First start the WPT's HTTP server from your wpt/ clone dir.
./wpt serve
Run a Lightpanda browser
zig build run -- --insecure-disable-tls-host-verification
Then you can start the wptrunner from the demo's clone dir:
cd wptrunner && go run .
Or one specific test:
cd wptrunner && go run . Node-childNodes.html
wptrunner command accepts --summary and --json options modifying output.
Also --concurrency define the concurrency limit.
releaseFast mode to make tests faster.
zig build -Doptimize=ReleaseFast run
Contributing
See CONTRIBUTING.md for guidelines. You must sign our CLA during the pull request process.
Why Lightpanda?
Javascript execution is mandatory for the modern web
Simple HTTP requests used to be enough for web automation. That's no longer the case. Javascript now drives most of the web:
- Ajax, Single Page Apps, infinite loading, instant search
- JS frameworks: React, Vue, Angular, and others
Chrome is not the right tool
Running a full desktop browser on a server works, but it does not scale well. Chrome at hundreds or thousands of instances is expensive:
- Heavy on RAM and CPU
- Hard to package, deploy, and maintain at scale
- Many features are not necessary in headless made
Lightpanda is built for performance
Supporting Javascript with real performance meant building from scratch rather than forking Chromium:
- Not based on Chromium, Blink, or WebKit
- Written in Zig, a low-level language with explicit memory control
- No graphical rendering engine
