Overview — what Trezor Bridge does and why it exists
Trezor Bridge is a small local service that runs on your computer to enable secure, controlled communication between a Trezor hardware wallet and wallet applications. Modern browsers and operating systems limit direct USB access for security reasons; Bridge acts as a trusted mediator so web apps and desktop clients can talk to the hardware device without exposing low-level USB interfaces to every webpage. It does not hold keys or sign transactions — it simply forwards messages between a client and the hardware. The critical security boundary remains: the device screen and physical confirmation buttons are the only trusted authority for approving sensitive operations.
How Bridge works (high level)
When installed, Bridge listens on a local loopback address and accepts well-defined API calls from authorized client software running on the same machine. The client negotiates a session, Bridge performs USB input/output with the connected Trezor device, and the device displays transaction details or addresses that must be confirmed by the user. The architecture separates the concerns of UI (desktop or web app) and custody (the hardware device), ensuring private keys remain on the device at all times.
Installation and configuration
Installing Bridge is simple: run the installer appropriate for your operating system, grant any requested privileges so it can register its local service, and follow the installer prompts. On Windows and macOS this typically registers a background service; on Linux you may need to handle udev rules or permissions to allow non-root access to USB devices. After installation the Bridge service should start automatically and remain running while your wallet app needs it.
When installing, use the official, vendor-supplied installer and verify checksums if they are provided. Avoid third-party downloads and unverified packages — supply-chain risks exist when an installer is tampered with.
Using Bridge with desktop and web apps
With Bridge running and the device connected, wallet software will detect the Trezor and allow account discovery, balance viewing, and transaction creation. For web applications, the app speaks to Bridge via the local API so the browser can request device operations without needing raw USB permissions. For desktop apps the flow is similar but may call Bridge directly. Always verify every address and transaction on the hardware device screen before confirming in the app.
A user story
You open a web wallet, connect your hardware device, prepare a transaction in the web UI, then sign on the Trezor device. The web UI shows the response once the device confirms. At no time do the private keys leave the hardware device.
Security model and best practices
Bridge reduces friction but does not remove the need for operational security. Follow these best practices:
- Install Bridge only from the official source and verify installer integrity where possible.
- Keep Bridge and wallet applications updated to receive security fixes.
- Use a trusted computer with minimal unnecessary software and minimal browser extensions for crypto activity.
- Always verify transaction details, recipient addresses, and amounts on the device screen before approving.
- Do not connect your hardware wallet to public or unknown machines.
Developer notes — integrating with Bridge
If you are building wallet software that integrates with Bridge, use the official client libraries and follow the documented protocol. Important integration points:
- Detect Bridge's running state and provide clear, actionable instructions if it is missing.
- Use clear UI states for "waiting for device confirmation" so users know when to check their device.
- Never attempt to sign transactions without explicit, informed user consent reflected in the UI.
- Implement graceful error handling for device disconnects, busy states, and permission issues.
From a privacy perspective, client apps should minimize telemetry and avoid sending unnecessary account data to external servers. If blockchain queries are required, provide options for advanced users to configure their own node or provider.
Troubleshooting common issues
Bridge not running or device not detected
Check that the Bridge service is active (system processes or system tray), reconnect the USB cable, and restart the wallet application. Rebooting the computer clears many transient errors. On Linux check udev rules and ensure your user has permission to access USB devices.
Permission or "device busy" errors
Another application may hold an exclusive connection to the device. Close other wallet or browser windows that might be connected and retry. If the problem persists, a system restart usually resolves stuck device handles.
Unexpected prompts or warnings
If you see unusual prompts asking for secrets or offering to install third-party drivers, stop and verify the origin of the prompt. Do not enter recovery seeds into any application. If a prompt is unclear, disconnect the device and consult trusted documentation before continuing.
Compatibility and platform notes
Bridge is supported on the main desktop platforms. Mobile environments are more restrictive since they rarely provide a long-running local service; mobile integrations often rely on native USB or Bluetooth stacks or use companion apps. Use a modern, up-to-date browser for web wallet interactions to avoid compatibility and security issues.
Advanced workflows
For higher assurance operations consider air-gapped or multisig workflows. Prepare unsigned transactions on an online machine, sign on an isolated machine with the hardware device, and broadcast from the online machine. Multisignature setups split signing authority across multiple devices to remove single points of failure.
Privacy considerations
Bridge performs local communication only and is not designed to transmit account or seed data off the machine. However, wallet apps often query third-party APIs for balances, prices, and history. Consider privacy implications of those providers and, if privacy is a priority, configure your wallet to use a personal node or trusted provider where possible.
FAQ
- Does Bridge ever see my private keys?
- No — private keys remain on the hardware device. Bridge forwards messages; it does not hold or export keys.
- Can I use Bridge on any computer?
- Technically yes, but you should only use computers you trust. Public or compromised machines can expose other sensitive data and increase risk.
- What if my wallet app asks me to install a browser plugin instead of Bridge?
- Prefer the official Bridge mediator whenever available. Be cautious about third-party plugins; only use widely reviewed and trusted solutions.
Closing recommendations
Trezor Bridge is a useful, low-privilege tool that makes hardware-wallet usage smooth across web and desktop applications while preserving the core security model. Install only official software, run Bridge on trusted machines, verify every on-device prompt, and keep software updated. For very large-value holdings, adopt additional workflows such as multisig or air-gapped signing and conduct periodic audits of backup and restore procedures. Those simple habits — verify, minimize exposure, and back up carefully — are the foundations of safe self-custody.