Overview

Trezor Bridge is intentionally minimal: it runs on the user’s machine, detects connected Trezor devices, and exposes a tightly-scoped API that browser applications can use to request actions such as retrieving public keys, composing transactions, or requesting signatures. Crucially, Bridge never has access to private keys — every signing operation requires explicit confirmation on the physical device.

Why Bridge matters

Web applications provide unmatched convenience, but browsers and web pages are higher-risk environments than hardware wallets. Bridge solves this by acting as a local mediator. It ensures the following security guarantees:

• Local signing only: Raw private keys remain on your Trezor device and never leave it.
• Origin context: Bridge attaches the requesting web origin to signing requests so you can see which site requested an action on your device.
• Least privilege: It exposes only the APIs necessary for wallet operations and includes session controls for granting or revoking site access.

Key features

• Cross-platform installers for Windows, macOS, and Linux (AppImage / DEB).
• Mutually authenticated, TLS-protected local communication between browser and Bridge.
• Origin binding and session management shown at device confirmation prompts.
• Support for PSBTs (Partially Signed Bitcoin Transactions) and other air-gapped/multisig workflows.
• Developer-friendly tools: localhost testing modes, verbose logs, and safe testnet options.

Installation & first run

Installation steps are simple and platform-specific details are available on the official Trezor website. A typical flow looks like:

1. Download Bridge from the official site and verify checksums where possible.
2. Install the package for your OS (Windows .exe, macOS .dmg, Linux DEB/AppImage).
3. Start Bridge; it typically runs in the system tray. When a dApp needs access, the browser will prompt and Bridge will mediate the request.

On first run, Bridge creates a secure local certificate to authenticate browser connections. For Windows this may require administrator approval; on macOS and Linux you may need to allow network or socket permissions.

Typical user flow with a dApp

When using a web wallet or dApp that integrates with Trezor via Bridge, the high-level flow is:

1. dApp detects Bridge and lists available devices.
2. User selects a device and grants permission via the browser prompt.
3. dApp constructs a signing request and sends it to Bridge.
4. Bridge forwards the request to the Trezor device and includes the web origin.
5. Device shows the origin and transaction/data details; the user confirms or rejects.
6. On approval, the signed result is returned to the dApp for broadcasting or verification.

Security best practices

Bridge is secure by design, but users should follow these guidelines to minimize risk:

• Only download Bridge from the official Trezor domain and verify checksums/signatures.
• Inspect the origin displayed on your Trezor device before approving any action; do not rely solely on the website UI.
• Run Bridge on trusted machines and avoid authorizing unknown or untrusted sites.
• Disable Bridge auto-start on shared or public computers and revoke site permissions when finished.
• Keep Bridge and device firmware up to date to receive security patches and improvements.

Developer & integration notes

Developers integrating Bridge should design clear UX that informs users what will be signed, why the action is needed, and which origin is requesting access. Recommended practices include:

• Show full transaction details in-app before calling Bridge; the device verification is a safety net — not the only UI.
• Use testnets and localhost modes during development to avoid risking real funds.
• Respect session scoping: request minimal, time-limited permissions and allow users to disconnect cleanly.
• Implement proper error handling and informative messaging for origin mismatches, device disconnects, or user rejection.

Troubleshooting common issues

Some common problems and quick fixes:

• Bridge not detected: Ensure Bridge is running in the system tray and restart the browser. On Windows, re-run the installer with admin privileges to ensure TLS binding is set up.
• Device not found: Try a different USB cable/port and ensure the device is unlocked (PIN entered). On Linux, check udev rules and permissions.
• Origin mismatch: If Bridge reports an origin mismatch, close the dApp and re-open from the proper domain. Never approve requests from unfamiliar origins.
• Stuck transactions or failed signatures: Verify transaction data on-device and check dApp logs. For complex workflows use PSBT export for manual or air-gapped signing.

Privacy & telemetry

Bridge collects minimal telemetry by default to help with crash reporting and usage metrics; this can be disabled in settings. Importantly, Bridge does not transmit seeds, private keys, wallet addresses, or transaction payloads to external servers — all signing operations remain local.

Advanced & enterprise use

Enterprises and power users can configure Bridge for managed deployments: preapproved origins, centralized installation scripts, logging, and policy-controlled updates. For high-security setups, use PSBT workflows and air-gapped signing to avoid exposing private keys to networked machines.

Closing summary

Trezor Bridge bridges the convenience of web-based wallets with the uncompromising assurance of hardware signing. By keeping private keys on-device, requiring on-screen confirmation, and providing origin-aware session controls, Bridge preserves user control while enabling the rich Web3 ecosystem. Always install Bridge from official sources, verify integrity where possible, and treat the device screen as the final arbiter before approving any action.