Trezor Bridge — The Secure Gateway to Your Hardware Wallet®

Introduction

Trezor Bridge acts as a bridge — literally and conceptually — between your computer's user-facing software and the secure world inside your Trezor hardware wallet. Hardware wallets are designed to keep private keys off internet-connected devices; Bridge does not change that model. Instead, it creates a reliable, authenticated, and minimal transport layer so applications like Trezor Suite or compatible browser tabs can instruct the device to sign a transaction, verify a message, or perform a firmware update while ensuring those commands are delivered over a trusted channel.

Without Trezor Bridge (or an equivalent transport layer), many browsers and operating systems block direct access to USB or require complicated manual configuration. Bridge simplifies the user experience while maintaining the security guarantees of on-device signing and explicit user confirmation.

Why Trezor Bridge is necessary

Modern operating systems and browsers implement strong sandboxing, permission models, and layered driver stacks to protect users. While this improves security overall, it also prevents straightforward device access for specialized hardware like Trezor. Trezor Bridge provides a small, locally-run helper that abstracts those platform differences: it manages USB/HID transport, offers a standardized local API for applications, and handles device discovery and reconnection logic. For end users, Bridge removes friction — for security architects, it centralizes a small, auditable surface that can be kept up to date and monitored.

Crucially, Trezor Bridge does not — and must not — ever access or transmit your recovery seed or private keys. Those elements stay inside the hardware wallet. Bridge's role is purely communication and device management.

How Trezor Bridge works — technical overview

At a high level, Trezor Bridge runs as a background process (daemon/service) on the user's computer. It opens a secure local channel (for example a localhost HTTP endpoint, IPC socket, or a secure WebSocket) that only trusted local clients can access. When a user opens Trezor Suite or a web page that integrates with Trezor's transport layer, the application communicates with Bridge over that local channel. Bridge then proxies commands to the Trezor device over USB or other transport mechanisms supported by the OS.

A typical flow looks like this:

1. Application asks Bridge to list attached devices.
2. Bridge detects Trezor, opens a session, and negotiates a secure channel.
3. Application constructs a transaction or request and sends it to Bridge.
4. Bridge forwards the request to the device. The device displays transaction details for the user to confirm.
5. User confirms on-device; device signs and returns the signature to Bridge.
6. Bridge returns the signature to the application, which broadcasts it to the network.

This flow ensures the critical act of approving a transaction happens physically on the Trezor device, and that the host cannot covertly cause the device to sign without the user's visible approval.

Security model — what Bridge does and doesn't do

Understanding what Trezor Bridge is allowed to do — and what it is explicitly not allowed to do — is essential. Bridge provides a minimal, auditable codebase for local transport. It should be treated as trusted infrastructure but kept as small and simple as possible.

Bridge responsibilities

• Detecting and enumerating Trezor devices attached to the host.
• Forwarding commands and responses between host applications and the Trezor device.
• Managing reconnection and session lifecycle to provide a smooth UX.
• Logging minimal, non-sensitive operational events for troubleshooting (optional and configurable).

Bridge limitations — what it must never do

• Store, transmit, or process recovery seeds or private keys.
• Perform signing or other cryptographic operations on behalf of the device.
• Expose network-accessible endpoints without explicit user consent or authentication.

These clear boundaries preserve the security model: keys remain on-device, signing requires physical confirmation, and Bridge remains an isolated helper program.

Installing Trezor Bridge — step-by-step

This section walks through a generic installation and verification path for Trezor Bridge. The exact installer and prompts vary by operating system; always install Bridge from official, verified sources in your production environment.

Windows

1. Download the Bridge installer for Windows.
2. Run the installer and accept UAC prompts if they appear.
3. When installation completes, restart your browser and open Trezor Suite or the start portal.

macOS

1. Download the macOS package and open it.
2. Drag the Bridge app to Applications if required and follow any security prompts in System Preferences → Security & Privacy.
3. Restart your browser and test device detection.

Linux

1. Download the appropriate package for your distribution (AppImage, .deb, .rpm, etc.).
2. Install and, if necessary, add udev rules to allow non-root access to USB devices.
3. Reload udev rules: sudo udevadm control --reload-rules && sudo udevadm trigger

After installation, verify Bridge is running and that Trezor Suite or your browser can detect and communicate with the device. Many applications include a diagnostics view to confirm transport connectivity.

Plugins, Connectors, and Integrations

While Bridge covers the transport layer, some environments benefit from optional connectors or plugins. These are small helper modules that provide additional integration points: for example, bridging corporate single-sign-on, routing local market data into the Suite, or applying organization-level policy checks before submissions reach the device.

Design principles for plugins

• Run locally and with limited privileges; avoid global system access unless required.
• Communicate with Suite or Bridge over authenticated, local-only channels.
• Be auditable — keep source code or build artifacts signed and verifiable.
• Never attempt to access recovery seeds or private keys; leave signing to the device.

Example plugin uses

• Enterprise policy enforcement (e.g., require two approvers for transactions above a threshold).
• Offline accounting export (export watch-only data to an internal ledger).
• Custom transport shims for unusual environments (VMs or restricted OS setups).

A plugin should be optional — users should be able to run Trezor Suite + Bridge without any plugins installed. Keep plugin interfaces minimal and well-documented to reduce risk.

Plugin skeleton (illustrative)

Below is a very small pseudocode example showing how a local plugin might communicate with a local Suite endpoint. This is illustrative only — production code must include authentication, error handling, and secure update mechanisms.

// Pseudo-plugin (Node.js style) — illustrative only
const net = require('net');
const client = net.connect({ path: '/tmp/trezor-suite.sock' });

client.on('connect', () => {
  client.write(JSON.stringify({ type: 'plugin.register', name: 'policy-enforcer' }));
});

client.on('data', (buf) => {
  const msg = JSON.parse(buf.toString());
  if (msg.type === 'transaction.prepare') {
    // Analyze transaction and optionally respond with policy verdict
    const allowed = checkPolicy(msg.transaction);
    client.write(JSON.stringify({ type: 'plugin.policy', allowed, notes: 'Checked by policy-enforcer' }));
  }
});