Overview
Trezor Bridge is a small, locally-run helper application that acts as a bridge between web-based cryptocurrency applications (like web wallets and interfaces) and a Trezor hardware wallet connected by USB. Instead of the browser directly accessing the device, the browser communicates with Bridge over an HTTP-based localhost API. The Bridge forwards those requests to the Trezor device using native USB APIs, enabling secure transaction signing and device management while keeping private keys isolated on the hardware.
The main purpose of Bridge is to provide a stable, cross-platform communication layer that works across operating systems and browser security models, especially when direct USB access from the browser is restricted or inconsistent. It is not a full wallet app — it is a communication helper that trusted wallet UIs use to interact with your physical device.
How it works (conceptually)
Conceptually Bridge runs a tiny HTTP server on your machine, typically bound to localhost. Web applications that know how to talk to Trezor will send requests to this server; Bridge then translates those requests into USB calls using the Trezor device protocol. Responses are routed back to the web app. Because private keys never leave the device, the sensitive cryptographic operations happen inside the hardware wallet and Bridge only passes messages.
This layered approach separates concerns: browsers and websites focus on UX and transaction construction, while Bridge and the Trezor firmware handle transport and cryptography. It also lets vendors ship updates for the communication layer independently of the hardware firmware.
Installation & security notes
Installing Bridge is typically straightforward — download the official installer for your operating system from the vendor's site and run it. Because Bridge listens on localhost, it is important to install it only from official sources. Treat it as trusted software; verifying signatures or checksums when provided reduces risk. After installation, the software normally runs when you plug in a Trezor device or on system start, and browser-based wallets will detect it.
From a security standpoint: Bridge by itself cannot extract private keys. Any web app that asks to communicate with your device will still require you to confirm actions on the device screen. Keep Bridge up to date, and uninstall/disable it if you stop using a Trezor for long periods. Avoid installing Bridge copies from unknown sources.
Troubleshooting tips
If a web wallet does not detect your Trezor, commonly helpful steps are:
- Ensure the device is unlocked and displays the home screen.
- Confirm Bridge is running (check system tray or process list).
- Try a different USB cable or port — data-only cables are required.
- Restart Bridge or reboot the machine to reset USB permissions if needed.
- Make sure your browser isn't blocking localhost connections or extensions.
If problems persist, consult official support resources and avoid applying random command-line fixes suggested by unknown sites.
Alternatives & evolution
Over time, wallet providers have added different transport options: native desktop wallets, browser extensions, and protocols using WebUSB or WebHID. Some interfaces use native apps that bundle device connectivity, while others rely on Bridge for consistent behavior across platforms. Choosing between them depends on desired workflow, platform, and security model.
Regardless of the method, the security model remains driven by the hardware device: private keys stored on the device and actions confirmed on its display are the core protections.
Good practices
- Only download Bridge from the official vendor site.
- Verify installers when signature/checksum is available.
- Keep firmware and helper tools up to date from trusted channels.
- Use a data-capable USB cable and avoid hubs that can interfere.
- When in doubt, ask support or consult the vendor's documentation.