@lerobot/web

interact with your robot in JS (WebSerial + WebUSB), inspired by LeRobot

🚀 Try the live demo →

Installation

# pnpm
pnpm add @lerobot/web

# npm
npm install @lerobot/web

# yarn
yarn add @lerobot/web

Quick Start

import {
  findPort,
  releaseMotors,
  calibrate,
  teleoperate,
  record,
} from "@lerobot/web";

// 1. find available robot ports (shows browser port dialog)
console.log("🔍 finding available robot ports...");
const findProcess = await findPort();
const robots = await findProcess.result;

if (robots.length === 0) {
  console.log("❌ no robots found. check connections and try again.");
  return;
}

// 2. connect to the first robot found
console.log(`✅ found ${robots.length} robot(s). using first one...`);
const robot = robots[0]; // already connected from findPort

// 3. release motors for manual positioning
console.log("🔓 releasing motors for manual positioning...");
await releaseMotors(robot);

// 4. calibrate motors by moving through full range
console.log("⚙️ starting calibration...");
const calibrationProcess = await calibrate({
  robot,
  onProgress: (message) => console.log(message),
  onLiveUpdate: (data) => console.log("live positions:", data),
});

// move robot through its range, then stop calibration
console.log("👋 move robot through full range, then stop calibration...");
// in a real app, you'd have a button to stop calibration
setTimeout(() => {
  calibrationProcess.stop();
}, 10000); // stop after 10 seconds for demo

const calibrationData = await calibrationProcess.result;
console.log("✅ calibration complete!");

// 5. control robot with keyboard
console.log("🎮 starting keyboard control...");
const teleop = await teleoperate({
  robot,
  calibrationData,
  teleop: { type: "keyboard" }, // or { type: "direct" }
});
teleop.start();

// stop control after 30 seconds
setTimeout(() => {
  teleop.stop();
  console.log("🛑 control stopped");
}, 30000);

How It Works

findPort() - Discovery + Connection in One Step

In the browser, findPort() handles both discovery AND connection testing. It returns ready-to-use robot connections:

// ✅ browser workflow: find and connect in one step
const findProcess = await findPort();
const robots = await findProcess.result;
const robot = robots[0]; // ready to use - already connected and tested!

Why no separate connectPort()? The browser's WebSerial API requires user interaction for port access, so findPort() handles everything in one user-friendly flow.

Need direct port connection? Use @lerobot/node which provides connectPort() for server-side applications where you know the exact port path (e.g., "/dev/ttyUSB0").

Core API

findPort(config?): Promise<FindPortProcess>

Discovers and connects to robotics hardware using WebSerial API. Two modes: interactive (shows port dialog) and auto-connect (reconnects to known robots).

Interactive Mode (Default)

First-time usage or discovering new robots. Shows native browser port selection dialog.

// User selects robot via browser dialog
const findProcess = await findPort();
const robots = await findProcess.result; // RobotConnection[]
const robot = robots[0]; // User-selected robot

// Configure and save robot for future auto-connect
robot.robotType = "so100_follower";
robot.robotId = "my_robot_arm";

// Save to localStorage (or your storage system)
localStorage.setItem(
  `robot-${robot.serialNumber}`,
  JSON.stringify({
    robotType: robot.robotType,
    robotId: robot.robotId,
    serialNumber: robot.serialNumber,
  })
);

Auto-Connect Mode

Automatically reconnects to previously configured robots without showing dialogs.

// Build robotConfigs from saved data
const robotConfigs = [];

// Option 1: Load from localStorage (typical web app pattern)
for (let i = 0; i < localStorage.length; i++) {
  const key = localStorage.key(i);
  if (key?.startsWith("robot-")) {
    const saved = JSON.parse(localStorage.getItem(key)!);
    robotConfigs.push({
      robotType: saved.robotType,
      robotId: saved.robotId,
      serialNumber: saved.serialNumber,
    });
  }
}

// Option 2: Create manually if you know your robots
const robotConfigs = [
  { robotType: "so100_follower", robotId: "left_arm", serialNumber: "USB123" },
  { robotType: "so100_leader", robotId: "right_arm", serialNumber: "USB456" },
];

// Auto-connect to all known robots
const findProcess = await findPort({
  robotConfigs,
  onMessage: (msg) => console.log(msg),
});

const robots = await findProcess.result;
const connectedRobots = robots.filter((r) => r.isConnected);
console.log(
  `Connected to ${connectedRobots.length}/${robotConfigs.length} robots`
);

RobotConfig Structure

interface RobotConfig {
  robotType: "so100_follower" | "so100_leader";
  robotId: string; // Your custom identifier (e.g., "left_arm")
  serialNumber: string; // Device serial number (from previous findPort)
}

Options

• robotConfigs?: RobotConfig[] - Auto-connect to these known robots
• onMessage?: (message: string) => void - Progress messages callback

Returns: FindPortProcess

• result: Promise<RobotConnection[]> - Array of robot connections
• stop(): void - Cancel discovery process

calibrate(config): Promise<CalibrationProcess>

Calibrates motor homing offsets and records range of motion.

const calibrationProcess = await calibrate({
  robot,
  onProgress: (message) => {
    console.log(message); // "⚙️ Setting motor homing offsets"
  },
  onLiveUpdate: (data) => {
    // Real-time motor positions during range recording
    Object.entries(data).forEach(([motor, info]) => {
      console.log(`${motor}: ${info.current} (range: ${info.range})`);
    });
  },
});

// Move robot through full range of motion...
// When finished recording ranges, stop the calibration
console.log("Move robot through its range, then stopping in 10 seconds...");
setTimeout(() => {
  calibrationProcess.stop(); // Stop range recording
}, 10000);

const calibrationData = await calibrationProcess.result;
// Save calibration data to localStorage or file

Options

• config: CalibrateConfig
  • robot: RobotConnection - Connected robot from findPort()
  • onProgress?: (message: string) => void - Progress messages
  • onLiveUpdate?: (data: LiveCalibrationData) => void - Real-time position updates

Returns: CalibrationProcess

• result: Promise<CalibrationResults> - Calibration data (Python-compatible format)
• stop(): void - Stop calibration process

Calibration Data Format

Python Compatible: This format is identical to Python lerobot calibration files.

{
  "shoulder_pan": {
    "id": 1,
    "drive_mode": 0,
    "homing_offset": 14,
    "range_min": 1015,
    "range_max": 3128
  },
  "shoulder_lift": {
    "id": 2,
    "drive_mode": 0,
    "homing_offset": 989,
    "range_min": 965,
    "range_max": 3265
  },
  "elbow_flex": {
    "id": 3,
    "drive_mode": 0,
    "homing_offset": -879,
    "range_min": 820,
    "range_max": 3051
  },
  "wrist_flex": {
    "id": 4,
    "drive_mode": 0,
    "homing_offset": 31,
    "range_min": 758,
    "range_max": 3277
  },
  "wrist_roll": {
    "id": 5,
    "drive_mode": 0,
    "homing_offset": -37,
    "range_min": 2046,
    "range_max": 3171
  },
  "gripper": {
    "id": 6,
    "drive_mode": 0,
    "homing_offset": -1173,
    "range_min": 2038,
    "range_max": 3528
  }
}

teleoperate(config): Promise<TeleoperationProcess>

Enables real-time robot control with extensible input devices. Supports keyboard control and direct programmatic movement, with architecture for future input devices like leader arms and joysticks.

Keyboard Teleoperation

import { teleoperate, KeyboardTeleoperator } from "@lerobot/web";

const keyboardTeleop = await teleoperate({
  robot,
  calibrationData: savedCalibrationData, // From calibrate()
  teleop: { type: "keyboard" }, // Uses keyboard controls
  onStateUpdate: (state) => {
    console.log(`Active: ${state.isActive}`);
    console.log(`Motors:`, state.motorConfigs);
  },
});

// Start keyboard control
keyboardTeleop.start();

// Access keyboard-specific methods
const keyboardController = keyboardTeleop.teleoperator as KeyboardTeleoperator;
await keyboardController.moveMotor("shoulder_pan", 2048);

// Stop when finished
setTimeout(() => keyboardTeleop.stop(), 30000);

Direct Teleoperation

import { teleoperate, DirectTeleoperator } from "@lerobot/web";

const directTeleop = await teleoperate({
  robot,
  calibrationData: savedCalibrationData,
  teleop: { type: "direct" }, // For programmatic control
  onStateUpdate: (state) => {
    console.log(`Motors:`, state.motorConfigs);
  },
});

directTeleop.start();

// Access direct control methods
const directController = directTeleop.teleoperator as DirectTeleoperator;
await directController.moveMotor("shoulder_pan", 2048);
await directController.setMotorPositions({
  shoulder_pan: 2048,
  elbow_flex: 1500,
});

// Stop when finished
setTimeout(() => directTeleop.stop(), 30000);

Options

• config: TeleoperateConfig
  • robot: RobotConnection - Connected robot from findPort()
  • teleop: TeleoperatorConfig - Teleoperator configuration:
    • { type: "keyboard", stepSize?: number, updateRate?: number, keyTimeout?: number } - Keyboard control
    • { type: "direct" } - Direct programmatic control
  • calibrationData?: { [motorName: string]: any } - Calibration data from calibrate()
  • onStateUpdate?: (state: TeleoperationState) => void - State change callback

Returns: TeleoperationProcess

• start(): void - Begin teleoperation
• stop(): void - Stop teleoperation and clear states
• getState(): TeleoperationState - Current state and motor positions
• teleoperator: BaseWebTeleoperator - Access teleoperator-specific methods:
  • KeyboardTeleoperator: updateKeyState(), moveMotor(), etc.
  • DirectTeleoperator: moveMotor(), setMotorPositions(), etc.
• disconnect(): Promise<void> - Stop and disconnect

Keyboard Controls (SO-100)

Arrow Keys: Shoulder pan/lift
WASD: Elbow flex, wrist flex
Q/E: Wrist roll
O/C: Gripper open/close
Escape: Emergency stop

releaseMotors(robot, motorIds?): Promise<void>

Releases motor torque so robot can be moved freely by hand.

// Release all motors for calibration
await releaseMotors(robot);

// Release specific motors only
await releaseMotors(robot, [1, 2, 3]);

Options

• robot: RobotConnection - Connected robot
• motorIds?: number[] - Specific motor IDs (default: all motors for robot type)

record(config): Promise<RecordProcess>

Records robot motor positions and teleoperation data using a clean function API that matches the patterns established by calibrate() and teleoperate().

import { teleoperate, record } from "@lerobot/web";

// 1. Create teleoperation first
const teleoperationProcess = await teleoperate({
  robot: connectedRobot,
  teleop: { type: "keyboard" },
  calibrationData: calibrationData,
});

// 2. Create recording with teleoperator
const recordProcess = await record({
  teleoperator: teleoperationProcess.teleoperator,
  videoStreams: {
    main: mainCameraStream,
  },
  robotType: "so100",
  options: {
    fps: 30,
    taskDescription: "Pick and place task",
  },
});

// 3. Start both processes
teleoperationProcess.start();
recordProcess.start();

// 4. Manage recording during operation
recordProcess.nextEpisode(); // Start new episode if needed

// 5. Stop recording and export
const robotData = await recordProcess.stop();
await recordProcess.exportForLeRobot("zip-download");

Options

• config: RecordConfig
  • teleoperator: WebTeleoperator - The teleoperator to record from
  • videoStreams?: { [name: string]: MediaStream } - Optional camera streams (e.g., { main: stream1, wrist: stream2 })
  • robotType?: string - Robot metadata (e.g., "so100")
  • options?: RecordOptions - Optional recording configuration:
    • fps?: number - Target frames per second (default: 30)
    • taskDescription?: string - Task description
    • onStateUpdate?: (state: RecordingState) => void - Recording state changes

Returns: RecordProcess

• start(): void - Start recording
• stop(): Promise<RobotRecordingData> - Stop recording and get data
• getState(): RecordingState - Current recording state
• getEpisodeCount(): number - Get total episodes
• nextEpisode(): Promise<number> - Start new episode
• clearEpisodes(): void - Delete all episodes
• addCamera(name: string, stream: MediaStream): void - Add camera dynamically
• exportForLeRobot(format?: "blobs" | "zip" | "zip-download"): Promise<any> - Export dataset

Browser Requirements

• chromium 89+ with WebSerial and WebUSB API support
• HTTPS or localhost
• User gesture required for initial port selection

Hardware Support

Currently supports SO-100 follower and leader arms with STS3215 motors. More devices coming soon.