Overview
Trezor Bridge is a lightweight local application that acts as a secure communication layer between Trezor hardware wallets and web/browser or desktop applications such as Trezor Suite. It provides a standardized transport for messages, handling USB and HTTP bridging so that web apps can interact with the device without needing specialized driver installation. Bridge keeps the communication local to your machine and translates browser requests into device‑level operations the Trezor can execute.
The aim of this guide is to provide a practical understanding of Bridge: why it exists, how it secures sign requests, how to install and configure it across platforms, and how developers or power users can integrate it into workflows.
How it works
At a high level, Trezor Bridge listens on a local port and exposes a secure API to authorized clients. When a web app (or desktop app) needs to talk to a Trezor device, it sends JSON‑RPC requests to Bridge. Bridge then forwards those requests to the device over USB (or other physical connection) and sends back the device responses. This indirection isolates browser contexts from directly accessing USB devices while enabling secure device operations.
Components
- Bridge daemon: runs on the host (Windows/macOS/Linux) and listens on a localhost port.
- Client libraries: web or desktop clients use standard libraries to format requests and handle responses.
- Device firmware: the Trezor device firmware implements the signing and verification logic and exposes a protocol that Bridge translates to/from JSON‑RPC.
Communication flow
- Client app constructs a request (e.g., "get addresses" or "sign transaction").
- Request sent to Bridge over a localhost HTTP endpoint secured by origin checks.
- Bridge forwards the request to the device over USB (using HID/USB stacks).
- Device prompts the user on the physical device for confirmation (display + buttons).
- User verifies and confirms on the device; device signs/executes the operation.
- Bridge relays the signed response back to the client app.
Security model
Trezor Bridge is designed to minimize exposure of sensitive operations. The security model has several key properties:
- Local-only transport: Bridge listens on localhost and does not expose endpoints externally by default, preventing network attackers from reaching it remotely.
- Origin checks: When used in browsers, Bridge validates the origin of requests to reduce cross-site request forgery risks.
- User presence: Sensitive operations require explicit physical confirmation on the device (button press and verification on-screen).
- Firmware verification: Bridge ensures the device firmware reports its identity; updates are applied only when user‑approved via Suite.
Together these controls ensure that even if a malicious web page attempts to request signing, the user must physically confirm the exact transaction contents displayed on the device to proceed.
Setup & installation
Bridge installers are available for Windows, macOS and Linux. Installation is straightforward but differs slightly by platform.
Windows
Run the installer executable and follow prompts. Bridge will register itself to start on demand and open a local port for client communication. You may need administrative permissions for initial install.
macOS
Open the downloaded package and drag Bridge to the Applications folder or run the installer. macOS may request permission to access USB devices; grant access when prompted.
Linux
Install the appropriate package for your distribution (deb/rpm) or use the tarball. You may need to add udev rules to grant non‑root access to the device nodes; follow the provided instructions to add rules to /etc/udev/rules.d/ and reload udev.
Post‑install
After installing, ensure Bridge is running. On first run, attach a Trezor device and verify that the Bridge status indicates the device is connected. If using a browser, allow the browser to talk to Bridge following the prompts and pay attention to origin warnings — ensure you trust the web app you are using.
Using Bridge with Trezor Suite and web apps
Most users will interact with Bridge indirectly via Trezor Suite. Suite handles device firmware checks, app management, and presents a clean UI for key operations. Advanced users may use web apps or developer tools that rely on Bridge for device communication. In all cases, always verify actions on the physical device screen.
Typical user flow
- Open Trezor Suite or a supported web app that uses Bridge.
- Connect your device and unlock it (enter PIN on device).
- Perform operations like creating accounts, sending transactions, or signing messages; verify each action on the device.
Troubleshooting common issues
Bridge not running
If Bridge is not running, try to launch it manually from your applications menu. Restarting the host machine can also help. On Linux, ensure the service is enabled and udev rules are in place.
Device not detected
Try a different USB cable and port. Use a direct USB connection and avoid hubs. Check for conflicting applications that might hold the USB resource.
Browser refuses to connect
Ensure Bridge is allowed to accept requests from the browser origin; clear cached permissions and retry. Use the browser console to inspect errors and check Bridge logs for details.
Permissions & udev rules (Linux)
Confirm the udev rules were added and reloaded. The rules should give a specific user group access to the Trezor device nodes. After updating rules, reconnect the device and restart Bridge.
Developer notes
Developers integrating with Bridge should use the provided client libraries and follow the protocol and origin restrictions. Typical integration steps include establishing the JSON‑RPC channel, handling device enumeration, and implementing appropriate error handling and timeout strategies.
Security considerations for developers
- Never assume the client environment is trusted; always require user confirmation on the device for signing operations.
- Use origin checks to prevent unauthorized pages from communicating with Bridge.
- Implement robust logging and informative error messages — help users distinguish between benign warnings and critical security prompts.
Sample request pattern
{
"type": "call",
"method": "getAddress",
"params": {"path": "m/44'/0'/0'/0/0"}
}
The above JSON demonstrates a typical call format; libraries will abstract much of this for you. The response will include the address data, which your client should verify on the device screen before use.
FAQ
Is Bridge required?
For browser-based interactions and convenient desktop integrations, Bridge is highly recommended. It simplifies device access and avoids the need for browser-specific USB permissions. In some contexts, alternative transports may be available, but Bridge provides the smoothest experience for most users.
Is Bridge safe?
Bridge is safe when used properly. Key safety practices include keeping Bridge on localhost, granting permissions only to trusted origins, and confirming all transaction details on the physical device. Bridge does not expose private keys — only the device can sign requests.
Can Bridge be disabled?
Yes — advanced users can stop or uninstall Bridge. However, doing so may limit the ability of web apps to communicate with the device. Trezor Suite bundles the necessary connectivity for most users and will guide through alternative setups if needed.
Best practices
- Keep Bridge and Trezor Suite up to date with official releases.
- Use direct USB connections and avoid public or untrusted machines for sensitive operations.
- Verify the origin and application requesting access; avoid granting permissions to unknown pages.
- Educate users to always confirm transaction details on the device before approving.
Final checklist
- Install Trezor Bridge for your platform and confirm the service is running.
- Connect your Trezor device directly and verify it appears in Bridge/Suite.
- Use Trezor Suite for firmware updates and to manage apps and accounts.
- When using web apps, grant permissions only to trusted origins and confirm on‑device.
- Regularly update Bridge and Suite and follow recovery seed best practices.