Trezor Bridge for Developers: API Integration Guide

1. Introduction

Trezor Bridge is an open-source communication layer enabling apps to interact securely with Trezor devices over USB or HID. As a developer, Bridge gives you local HTTP and WebSocket endpoints so you can send commands, query device information, and perform signing operations — all while keeping private keys inside the hardware wallet.

This guide walks through key endpoints, integration tips, and example snippets to help you embed Trezor support in your web or desktop application.

2. Architecture Overview

The Bridge acts as a **local service** listening at 127.0.0.1:21325. When an app like Trezor Suite or your own project requests device data, the Bridge mediates communication, serializing messages via the protobuf protocol.

• Bridge ⇄ Browser communication: HTTP / WebSocket
• Bridge ⇄ Trezor Device communication: USB HID
• All requests validated through device descriptors and JSON schemas

For developers, this means you can build decentralized apps without exposing any sensitive operations outside the user’s device.

3. API Endpoints

The Bridge exposes a few local API endpoints accessible from browsers or native apps:

• GET /status/ — Returns Bridge status and connected devices.
• POST /call/ — Sends serialized commands to the device.
• GET /devices/ — Lists available connected Trezor units.

curl http://127.0.0.1:21325/status/
{
  "version": "2.0.31",
  "devices": [
    {"path": "bridge:0001:002","session": null}
  ]
}

The above response confirms that Bridge is running and ready to accept calls.

4. JavaScript Integration Example

You can connect to the Bridge using standard JavaScript APIs. Here’s a minimal example:

async function getBridgeStatus(){
  const res = await fetch("http://127.0.0.1:21325/status/");
  const data = await res.json();
  console.log(data);
}
getBridgeStatus();

This simple call helps verify local service health before initiating wallet sessions. For more complex apps, use the Trezor Connect library — it handles low-level communication automatically through Bridge.

5. Working with Trezor Connect

Trezor Connect provides a high-level abstraction over the Bridge API, allowing developers to focus on user flow instead of protocol details.

import TrezorConnect from 'trezor-connect';

TrezorConnect.init({
  connectSrc: 'https://connect.trezor.io/9/',
  lazyLoad: true,
});

TrezorConnect.getPublicKey({ path: "m/44'/0'/0'" })
  .then(response => console.log(response));

This approach ensures that even browser-based dApps remain secure, since all cryptographic actions stay on the device.

6. Handling Sessions

Bridge uses session tokens to manage concurrent access. Each app that connects requests a session; only one app can actively communicate with the device at a time. To release a session, send a DELETE /release/<session_id> request.

7. Security Considerations

Trezor Bridge enforces strict local-only access. Browsers or apps must originate from HTTPS-verified domains such as suite.trezor.io. External IPs cannot call local endpoints, reducing the chance of remote exploits.

• Always run Bridge from official binaries.
• Sign outgoing transactions only after manual confirmation on the device screen.
• Use HSTS and CSP headers in web projects integrating Trezor Connect.

8. Testing & Debugging

Developers can debug Bridge communications using standard tools:

• Check 127.0.0.1:21325/logs/ for verbose device responses.
• Use Trezor Learn articles for device message references.
• Run Bridge with the --debug flag to see detailed transport logs.

9. Building Cross-Platform Apps

Bridge supports Windows, macOS, and major Linux distributions. Cross-platform developers can embed it in Electron or Python apps:

# Python example using requests
import requests
r = requests.get('http://127.0.0.1:21325/status/')
print(r.json())

Electron developers can spawn Bridge as a background process bundled within the application installer. Just ensure it updates automatically through the official channel.

10. Future-Proofing Your Integration

Trezor Bridge evolves alongside new firmware and browser APIs. Always monitor release notes for updates, and subscribe to the developer newsletter for SDK changes. Version-pin your dependencies and verify checksum integrity to maintain consistency across deployments.

Following these practices ensures your app remains secure, performant, and compatible with the latest Trezor ecosystem.

Conclusion

Trezor Bridge empowers developers to build secure crypto applications that directly interface with hardware wallets while keeping private keys offline. By leveraging its local API and integrating through official resources, you can extend wallet functionality safely and transparently. Start experimenting today by visiting trezor.io/bridge and exploring the source at GitHub.