Introduction
Trezor Bridge is a lightweight background service that enables secure communication between your Trezor hardware wallet and web applications running in your browser. It replaces the older web USB approach for devices and provides a reliable transport layer so wallets, explorers, and dApps can talk to the physical device to request addresses, sign transactions, and verify device fingerprints.
This guide explains what Bridge does, why it's necessary, how to install and harden it, common troubleshooting steps, developer integration notes, and how it fits into a secure crypto workflow.
What is Trezor Bridge?
At a high level, Trezor Bridge runs as a small native application on your computer (Windows, macOS, Linux) and exposes an HTTP(s)-like API on a loopback address. Browser-based web apps can call into Bridge to enumerate connected Trezor devices, exchange APDU commands, and coordinate user confirmations on-device. Because browsers limit low-level USB access for security reasons, Bridge acts as an authorized intermediary that maintains a secure channel to the hardware and only exposes limited, well-defined endpoints to the browser context.
Note: Bridge is not a cloud service — it runs locally. No private keys or seed phrases leave your device or computer as part of the Bridge operation. The service only forwards encrypted device commands and responses.
Why use Bridge — reasons and benefits
- Compatibility: Enables modern browsers to talk to Trezor without relying on experimental web USB APIs that vary between browsers.
- Stability: Provides a consistent interface across OSes and browser versions.
- Security: Limits exposure by running locally and by requiring user interaction on the device for all sensitive actions.
- Developer friendliness: Exposes a simple API for apps to implement device features like firmware updates, passphrase handling, and transaction signing.
Installing Trezor Bridge
- Download Bridge from the official Trezor website. Always verify you are on the correct domain (trezor.io) and avoid third-party mirrors.
- Run the installer and follow on-screen steps. On macOS and Windows, Bridge installs a small background service that listens on a loopback port.
- After installation, open your browser and visit the web wallet or app; the web app should detect Bridge and prompt to connect to the device.
- For Linux, follow distribution-specific instructions and ensure your user has permission to access USB devices (udev rules on many distributions).
If you're using a mobile device, Trezor Bridge is not used — mobile apps typically use Bluetooth (for devices that support it) or platform-specific flows.
Security considerations & hardening
Bridge is designed with the principle of least privilege: it runs locally, only accepts connections from the same machine, and acts as a conduit rather than a vault. Still, follow these hardening practices:
- Install from official sources: Only download Bridge from trezor.io; verify signatures when provided.
- Keep Bridge updated: Updates often include bug fixes, security improvements, and better device support.
- Limit exposure: Bridge listens on loopback (localhost) by default — do not change it to an external interface. If you do any advanced configuration, ensure proper firewall rules are in place.
- Verify web apps: Only connect Bridge to trusted web apps and dApps. Treat browser tabs like untrusted processes: they can request actions but cannot complete them without you approving on the device screen.
- Use OS protections: Keep your OS and browser up-to-date, enable antivirus/anti-malware tools, and avoid running unknown code while your hardware wallet is connected.
Using Bridge in everyday workflows
Typical user flows with Bridge include: retrieving receiving addresses, signing transactions, confirming device fingerprints during setup, and performing firmware updates. The user experience is: open a web wallet, connect your device using Bridge, approve prompts on the Trezor screen, and the web app receives signed transactions to broadcast.
Best practice: Always verify critical transaction fields on the device display (recipient, amount, fee) before approving. Bridge merely forwards the request — the device screen is your ultimate source of truth.
Troubleshooting common Bridge issues
Bridge not detected: Ensure the Bridge service is running. On Windows, check Services; on macOS, look for the background process; on Linux, verify the installed package and udev rules.
Browser fails to connect: Try restarting the browser, clearing site permissions, or using a different browser. Ensure no other software is capturing USB (e.g., virtualization tools or alternate wallet services).
Device not listed: Try a different USB cable and port, avoid hubs, and ensure the device is unlocked (PIN entered) when attempting operations.
Developer integration notes
If you build web apps that interact with Trezor via Bridge, follow these guidelines:
- Use the official Trezor Connect library when possible — it abstracts Bridge transport details and provides helpers for common flows like signing and account discovery.
- Gracefully handle Bridge unavailability: provide clear instructions, a link to download Bridge, and retry mechanisms.
- Respect privacy — request only the permissions and data you need. Avoid collecting unnecessary public keys or addresses unless the user explicitly consents.
- Verify device UX — always prompt users to check the physical device for confirmations and show the exact fields they should verify.
Alternatives & when to choose them
For some advanced users and apps, alternative connection methods exist: native desktop apps using HID APIs directly, or air-gapped signing with PSBT/qrcode flows for the most paranoid workflows. Bridge offers convenience and broad compatibility; choose alternatives when you need complete air-gap separation or when deploying custom native integrations.
Final recommendations
- Always download Bridge from official sources and keep it updated.
- Never enter your seed phrase into any software — recovery should occur on a hardware device or trusted recovery environment only.
- Verify transaction details on the Trezor device before approving any signing action.
- Consider using dedicated browsing environments for crypto operations if you handle large-value transactions regularly.