Trezor Bridge — The Secure Gateway to Your Device®

Executive summary

Trezor Bridge is intentionally simple: it acts as a local, encrypted transport between applications and the Trezor device. It solves real-world compatibility problems by providing a consistent API, while preserving the core hardware security guarantees that make Trezor devices reliable. Bridge never holds or transmits private keys — it only relays commands and signed responses, and it requires user approval for every sensitive action on the physical device.

Why Bridge exists

Web browsers limit direct access to hardware for security reasons. Although browser APIs such as WebUSB and WebHID reduce friction, they vary in support and behavior across platforms and browser versions. Trezor Bridge provides a uniform, cross-platform solution that avoids these inconsistencies while keeping the device's security boundary intact. It allows both web-based wallets and native apps to interact reliably with Trezor devices without exposing key material to the host system.

How Bridge operates — technical overview

At a high level, Bridge runs as a background service on the user’s machine and exposes a local HTTPS endpoint bound to the loopback interface (localhost). Applications connect to this endpoint and send structured JSON requests. Bridge translates these requests into USB/HID commands that the Trezor device understands. After the device processes the request and — if required — the user confirms the operation, Bridge sends the response back to the requesting application. This flow preserves end-to-end user consent and isolation of cryptographic operations.

Message flow

1. An application requests device discovery or a signing operation via Bridge’s local HTTPS API.
2. Bridge checks permissions, forwards the request to the Trezor device over USB/HID, and waits for a response.
3. The device prompts the user (showing transaction data, addresses, or other details) for manual confirmation.
4. Once the user approves, the device signs or performs the requested operation and returns the result to Bridge.
5. Bridge relays the result to the original application for further processing (broadcasting, display, etc.).

Security guarantees

Bridge was designed with careful security trade-offs in mind. It provides the following guarantees:

• Key isolation: The private keys remain on the Trezor device. Bridge cannot extract or use them independently.
• Explicit user consent: Signing or sensitive operations require physical confirmation on the device itself.
• Local-only exposure: Bridge listens only on local interfaces. It does not expose Trezor to remote networks under default installation.
• Minimal footprint: Bridge intentionally performs only transport duties; it avoids unnecessary features that would expand its attack surface.

Despite these protections, the security of the overall setup depends on the host system. A compromised computer can still influence or manipulate what the user sees in the wallet UI; that’s why verifying transaction details on the device screen is critical.

Installing Bridge safely

Follow these steps to install Bridge with confidence:

1. Open the official Trezor website in your browser and navigate to the download page.
2. Select the correct Bridge installer for your operating system (Windows, macOS, or Linux).
3. Download the installer and — if checksums or signatures are provided — verify them against the values posted on the official site.
4. Run the installer. Administrative privileges are typically required to register the Bridge service and create the local endpoint.
5. After installation, restart your browser and any wallet applications to ensure they detect the Bridge service.

Note: Avoid installing Bridge packages from third-party mirrors or forums. If you see unexpected installation prompts, double-check the origin of the download.

Updating and maintenance

Updates to Bridge include security fixes, new device support, and compatibility improvements. Keep Bridge up to date by either re-running the latest installer from the official website or enabling in-place updates if offered. Regular system updates (OS and browser) complement Bridge updates and help maintain a secure environment.

Troubleshooting checklist

Many connectivity problems have straightforward fixes. Work through this checklist before seeking support:

• Confirm Bridge is running: look for its icon in the system tray/menubar or check running processes.
• Restart the browser and the Bridge service after installing or updating.
• Verify the USB cable is data-capable and not a power-only cable. Try another port or cable if the device is not detected.
• Close other programs that may monopolize USB access (virtual machines, other wallet software).
• On Linux, ensure udev rules are installed and that your user has permissions for USB devices; the installer often configures this automatically but some distros require manual steps.
• If you encounter certificate errors, update Bridge and consult platform-specific instructions to trust the local certificate used by Bridge’s HTTPS endpoint.

Common error scenarios

Permission denied or certificate trust issues

Browsers enforce strict certificate policies even for localhost. If a browser blocks the Bridge endpoint, update Bridge or follow instructions to add the local certificate to your OS/browser trust store. Avoid disabling certificate checks permanently—fix the root cause instead.

Device shows a different application or unexpected prompt

If the Trezor screen displays a prompt you don’t recognize, disconnect and re-evaluate the calling application. Only approve actions that you initiated and understand. If something looks suspicious, cancel the operation.

Developer notes & integration guidelines

Developers integrating Bridge should use official libraries and follow documented APIs. Best practices include:

• Abstract device discovery and session management through supported SDKs to reduce compatibility issues.
• Respect user privacy — never transmit seeds, passphrases, or other secrets to remote servers.
• Implement clear UI paths for users to cancel operations and recover from failures gracefully.
• Keep error messages actionable (suggest steps like reconnecting the device, checking cables, or updating Bridge).

Best practices for end users

• Always verify addresses and amounts on the Trezor screen before approving a transaction.
• Store your recovery seed offline in one or more safe locations and never type it into a computer or website.
• Use the official Trezor Suite or well-known wallet apps that explicitly support Bridge.
• Keep Bridge, your browser, and your OS up to date to reduce exposure to vulnerabilities.
• When possible, avoid using public or untrusted machines to access your hardware wallet.

Getting help and reporting issues

If you experience persistent problems, consult the official Trezor support pages, community forums, or open a support ticket. When reporting an issue, include details such as OS version, Bridge version, steps to reproduce, and any logs generated — this helps the development team diagnose and fix problems faster.