Trezor Bridge — Desktop bridge for Trezor hardware wallets

Purpose and role

Hardware wallets like Trezor separate private key storage from the internet. To send commands (for instance to sign a transaction) a desktop bridge is often necessary because modern browsers limit direct access to USB or HID devices for security or compatibility reasons. Trezor Bridge acts as that intermediary: it listens locally on your machine and exposes a secure channel that trustworthy web apps can use to send messages to your Trezor device.

How Trezor Bridge works (high level)

Trezor Bridge typically installs a small background service and a local HTTP(S) endpoint. When a web application wants to interact with your device, it either detects Bridge automatically or the user authorizes the connection. Bridge then proxies messages from the web app to the Trezor device over USB (or other supported transport), and returns structured responses. This architecture isolates hardware-level communication from the browser environment and provides a versioned, consistent protocol the web side can rely on.

Installation and supported platforms

Supported OS: Windows (incl. legacy), macOS, Linux.

Installing Bridge is intentionally simple. Typical steps include downloading the installer package from the official source, running the installer, and granting the OS any required permissions. For Linux, packages or a tarball may be available for manual installation. After installation, Bridge starts a background service and usually adds a small icon or system tray entry to indicate its state.

Note: Always download Bridge from the official distribution channel or the vendor's official website. Using unofficial binaries risks supply-chain compromise.

Security model

Trezor Bridge is designed to be a minimal, single-purpose piece of software. Security best practices to keep in mind:

• Source verification: Verify downloads via checksums or digital signatures when provided by the vendor.
• Least privilege: Bridge runs with minimum necessary privileges; avoid running untrusted processes with elevated permission where Bridge is installed.
• Device confirmation: Critical actions always require confirmation on the physical Trezor device. Bridge cannot bypass the need to physically confirm transactions or reveal sensitive information protected by the device PIN/seed.
• Local-only communication: The Bridge establishes local communications between the browser and the device; it should not forward private keys or sensitive data to external servers.

Common use cases

Typical scenarios where Bridge is used include:

• Using Trezor Suite web app to manage accounts and sign transactions.
• Third-party wallet integrations that require hardware signing through a browser.
• Developers building web-based dApps that require deterministic, device-backed signatures.

Developer integration (example)

The typical integration pattern is: detect Bridge, request a connection, and exchange JSON-like messages over a defined protocol. Below is a simplified pseudo-example to illustrate the idea — real production code should use the official SDK or libraries.

// simplified pseudo-code for establishing a connection
const bridgeUrl = 'http://127.0.0.1:21325';

async function pingBridge(){
const r = await fetch(`${bridgeUrl}/api/bridge/ping`, {method: 'GET'});
return r.ok;
}

async function getDeviceInfo(){
const r = await fetch(`${bridgeUrl}/api/bridge/devices`);
const devices = await r.json();
return devices;
}

Real integrations should follow the official API, handle errors, and not assume the bridge will always be present. Offer clear UI to guide the user to install or enable Bridge if it's missing.

Troubleshooting

Common issues and steps to resolve them:

• Bridge not running: Check the system tray or services list, or try restarting the Bridge service/process.
• Browser can't see Bridge: Ensure the browser page is served over HTTPS when required, and that any necessary permissions for local connections are granted.
• Permission errors on Linux: Some Linux distributions require udev rules for USB devices; ensure those rules are installed and re-login or reboot after installing them.
• Old Bridge version: Update to the latest bridge release if experiencing compatibility problems with new firmware.

Privacy considerations

Bridge itself is not intended to transmit personally identifying information to remote servers. However, web apps you connect with may collect metadata about your activity. Be mindful of the following:

• Only connect to websites you trust — malicious web pages can attempt to interact with any local Bridge that is listening.
• Review the privacy policy of applications that integrate with your device.
• Prefer self-hosted or audit-friendly software when managing large sums or when privacy is a priority.

Upgrades and compatibility

Bridge versions occasionally update to support new firmware features, fixes, or platform changes. When upgrading, make sure to:

• Read the release notes for breaking or notable changes.
• Ensure your Trezor device firmware is compatible with the Bridge version you install.
• Back up your recovery seed before performing firmware updates — firmware upgrades on the device itself may require reboots that cause the device to request recovery in certain edge cases.

Alternatives to Bridge

Some platforms and browsers support direct WebUSB or HID access. These alternatives can eliminate the need for a separate bridge component but have different security and compatibility trade-offs. Using a native bridge often offers the most stable cross-browser support without relying on experimental browser features.

Best practices for end users

• Download Bridge only from the official source and verify signatures when available.
• Keep your operating system and Bridge installation up to date.
• Never share your recovery seed or private keys — Bridge does not need to know them and cannot recover them for you.
• Confirm all transactions on the device screen; do not approve actions you didn't initiate.

FAQ

Q: Is Bridge required to use a Trezor?

A: Not always. Some native apps, mobile apps, or direct browser APIs can speak to the device without Bridge. However, for many web-based flows, especially on desktop, Bridge is the recommended and supported transport.

Q: Will Bridge send my seed or PIN anywhere?

A: No. Bridge is simply a conduit for messages between your browser and the device. The private key material and PIN entry/validation are handled entirely on the device itself and are never transmitted to remote servers by Bridge.

Q: I uninstalled Bridge — will my Trezor still work?

A: The physical device will remain functional, but web apps that expect Bridge may not be able to communicate with it until you reinstall or use an alternative transport.

Sample HTML snippet to detect Bridge

<!-- simple detection ping -->
<script>
async function detectBridge(){
try{
const r = await fetch('http://127.0.0.1:21325/bridge/ping');
if(r.ok) console.log('Bridge reachable');
else console.warn('Bridge not reachable');
}catch(e){
console.error('Bridge detection error', e);
}
}
window.addEventListener('load', detectBridge);
</script>

Wrapping up

Trezor Bridge fills an important gap between modern browser security models and the needs of hardware wallets. By running a controlled local service, it enables web applications to leverage Trezor devices for secure signing and account management while preserving the device-based security model. Whether you're an end user installing Bridge for the first time or a developer integrating Trezor support into your web app, understanding how Bridge operates and how to troubleshoot it will make for a smoother experience.

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