Trezor Bridge — The Secure Gateway to Your Hardware Wallet®

Introduction

Trezor Bridge plays a critical role in the Trezor ecosystem. It is the local relay — a small, trusted process running on your computer that safely brokers communications between Trezor hardware wallets and desktop or browser-based applications such as Trezor Suite and compatible web wallets. Bridge ensures that low-level USB interactions and device protocols are handled outside of the browser’s sandbox, reducing attack surface and providing a stable API for developers.

Why Bridge exists — a short history

Browsers have progressively tightened access to system resources to protect users from malicious web content. While WebUSB and other browser APIs exist, they have limitations, inconsistent support across platforms, and can introduce security ambiguities. Bridge was introduced to provide an explicit, auditable, and consistent local interface that works across operating systems and across classic desktop and web workflows. It allows Trezor to require on-device confirmations for sensitive operations while enabling developers to build powerful integrations without reinventing USB stacks.

Architecture & how it works

At a high level, Bridge is a lightweight background service that exposes HTTP/JSON endpoints on localhost and listens for connections from authorized clients. When a client requests an action (for example, to enumerate devices or to sign a transaction), Bridge validates and forwards the request to the connected Trezor device using platform-specific USB drivers. The device then prompts the user to verify and confirm the requested operation on the physical screen. This hardware confirmation is essential: it prevents remote or background software from signing transactions without explicit user approval.

Core components

• Local control plane: HTTP/JSON endpoints bound to localhost for status, enumeration, and control operations.
• USB transport layer: Platform adapters that manage USB device access across Windows, macOS and Linux.
• Authorization & pairing: Mechanisms that ensure clients can be paired or authorized to communicate with Bridge in a controlled manner.
• Update manager: Responsible for applying Bridge updates securely, usually via signed installers or in-app prompts.

Installation & setup

Installing Bridge is straightforward but should be done carefully to avoid phishing or tampered binaries. Below are recommended steps.

Security best practices

Bridge is secure by design but depends on the broader security of the host system and user behavior. Follow these practical recommendations:

1. Source verification

Only download Bridge from the official domain. Bookmark that URL and avoid search results that mimic the official site. If you are in a corporate environment, use an internal mirror after verifying the publisher signatures.

2. Keep Bridge updated

Enable automatic updates or routinely check for new releases. Updates sometimes contain security hardening and support for new device firmware versions. Test updates in a controlled environment if you manage many machines.

3. Local network hygiene

Bridge listens on localhost; avoid exposing its ports via port forwarding, reverse proxies, or other network tricks that may make it accessible from untrusted networks. Bridging localhost to the outside world can leak sensitive endpoints and should be avoided.

4. Principle of least privilege

Bridge and the applications that consume it should run with the minimum privileges required. Avoid running wallets or tooling as an administrator/root user unless absolutely necessary.

5. Verify on-device

No matter how secure your host, the device screen is the final arbiter. Always verify transaction outputs, addresses, and amounts on the Trezor device before approving.

Troubleshooting common issues

• Bridge not running: Restart the Bridge service and the host application. On Windows, check Services; on macOS, check Activity Monitor; on Linux, use systemd or process tools. Reinstall if the service fails repeatedly.
• Multiple Bridge instances: Ensure only one instance of Bridge is running. Two instances can conflict and prevent proper device enumeration.
• USB permission errors: On Linux, confirm udev rules are installed; on macOS, ensure the app has permission to access USB devices and that you're not blocking kernel extensions needed for some drivers.
• Device detected but not responsive: Try a known-good USB cable, avoid hubs, and try different ports. Test device with the official desktop Suite to isolate the problem.
• Corporate network interference: Some security appliances or endpoint protection software may block localhost ports or loopback traffic. Whitelist Bridge or work with IT to allow local loopback communication.

Developer integration & best practices

For application developers integrating Trezor support, Bridge offers a reliable transport. Respect the security guarantees: never request a user's seed, minimize surface area for signing operations, and design UIs that guide users to verify actions on the device.

Recommended developer flow

1. Detect Bridge on the local machine and prompt the user to install it if missing.
2. Enumerate connected devices and present clear labels to users (device model, firmware version).
3. When initiating a transaction, show a detailed summary in the host app and instruct the user to verify the same details on the Trezor screen.
4. Handle errors gracefully: present actionable messages (e.g., "Reconnect device", "Install udev rules", "Check cable").

Privacy considerations

Bridge itself does not transmit private keys or recovery seeds over the network. However, it can log diagnostics and metadata that may reveal transaction timing or device identifiers. Treat logs as sensitive information and sanitize them before sharing with support. If you are concerned about telemetry, review Bridge settings and documentation for options to limit or inspect diagnostics before sending.

Enterprise deployment

Organizations adopting hardware wallets at scale should plan for controlled Bridge deployment and lifecycle management. Consider the following checklist:

• Host verified installers internally and sign them for additional assurance.
• Test Bridge updates in staging environments before rolling out to production endpoints that manage funds.
• Define change control, incident response, and recovery procedures for compromised hosts.
• Use role separation—limit which personnel can restore seeds or perform high-risk actions.

Advanced topics

Pairing & authorization models

Some integrations implement pairing mechanisms to avoid accidental access by untrusted local applications. Pairing can involve user confirmation on the device and the host, providing a record of authorized client instances that may interact with Bridge.

Alternate transports

While Bridge is the canonical local transport, some advanced setups may use native drivers or operate in constrained environments where Bridge isn't available. In these cases, ensure any alternate transport preserves on-device verification and does not expose private keys to host processes in plaintext.

Release cadence & support

Bridge updates follow device and Suite releases. Subscribe to official release notes and security advisories for the most current information. When encountering unexpected behavior that may indicate a security issue, collect minimal, non-sensitive diagnostics and report through official channels rather than posting seeds or raw logs publicly.

FAQ

Practical checklist — before connecting

• Download Bridge from the official vendor site — verify URLs and, when possible, checksums.
• Install and verify the Bridge service is running and reachable on localhost.
• Connect your Trezor device directly to a USB port (avoid hubs) and confirm prompts on-device.
• Use the official Suite or a trusted web wallet and always verify transaction details on the device screen before approval.