Overview
Trezor Bridge is an application that enables secure, reliable communication between a Trezor hardware wallet and a user's web browser or desktop wallet software. It acts as a local bridge, translating messages between the USB device and wallet software over well-defined, authenticated channels. For users and integrators, Bridge significantly improves the user experience by removing direct browser USB compatibility problems and offering a consistent API across platforms.
Why a bridge?
Browsers and operating systems change rapidly. Direct USB access varies by platform and browser capability. A dedicated local service — the Bridge — provides a stable interface, handles device enumeration, manages firmware-aware protocol negotiation, and centralises security checks so that web apps don't have to implement complex device drivers.
Key benefits
- Cross-platform compatibility (Windows, macOS, Linux).
- Uniform API for web and native apps.
- Automatic updates and version compat checks.
- Isolated process to reduce exposure to malicious websites.
- Improved UX for device pairing and detection.
Architecture & Communication Flow
High-level components
The Bridge typically consists of these components: the Bridge daemon (local service), a browser extension or web app connector, the host OS USB stack, and the Trezor device firmware. Communication uses short, authenticated messages; the Bridge mediates and may perform version checks and request confirmation to ensure the device is in a safe state for requested operations.
Message lifecycle (simplified)
- Wallet app sends JSON-RPC (or similar) request to Bridge over local HTTP(s) or named pipe.
- Bridge authenticates the caller where applicable and translates the call to the binary device protocol.
- Bridge sends command to the Trezor device over USB (or WebUSB when available and secure).
- Device processes request and returns a response signed or confirmed as needed.
- Bridge packages the response and forwards it to the wallet app.
Design considerations
Latency is kept minimal by batching or streaming protocol frames where possible. Privacy considerations include limiting metadata exposed to the host and ensuring the Bridge does not leak device-only identifiers to third-party web apps without consent.
Security Model
Principle of least privilege
The Bridge should offer the smallest interface necessary to accomplish each task. For example, a request that only needs to read a public address should never be able to trigger signing operations. Permissions and user confirmations on the device are the ultimate defense.
Device-level confirmations
All sensitive operations (transaction signing, seed export) require explicit confirmation on the Trezor device. Even if the Bridge or host is compromised, the attacker cannot sign transactions without the device's user approving the action on the hardware screen.
Transport security
The local channel between Bridge and applications should be authenticated. Many implementations use a local HTTP server with CORS and token-based auth, or native IPC mechanisms. Bridge must verify origins or require pairing tokens to prevent silent access from malicious pages.
Update & integrity
Bridge releases must be signed and verified. Regular updates include security patches and protocol improvements; automated update mechanisms help protect users, but signing ensures only official binaries are accepted.
Integration & Best Practices
For Wallet Developers
- Use official Bridge API libraries where available rather than reimplementing the USB protocol.
- Implement strict origin checks and token pairing flows when interacting with local Bridge endpoints.
- Gracefully handle version mismatches — prompt users to update Bridge rather than failing silently.
For End Users
- Download Bridge only from official sources and keep it up to date.
- Verify download signatures when possible and use official installers.
- Use device confirmations — never approve unexpected signing requests on the device screen.
Troubleshooting tips
If the device is not detected: restart the Bridge service, reconnect the device, check OS USB permissions, and consult official support documentation. For persistent issues, reinstalling the Bridge from an official source often resolves driver/compatibility problems.
Developer tools
Most Bridge distributions include diagnostics and verbose logging. Use those logs when filing a bug report and avoid posting private keys or seed material in public bug trackers.
Conclusion
In short, Trezor Bridge is a focused, local service that simplifies and secures communication between wallet software and Trezor hardware. Its role is to provide a stable, auditable surface for apps to interact with devices; its security depends on careful design, user confirmations on hardware, and strict handling of local authentication and updates.
Below (right) you will find official links for download, documentation, support, and repositories to get started safely. Use them as your canonical sources.