Introduction
Trezor Bridge is the official local helper that creates a stable, secure communication channel between Trezor hardware wallets and desktop/browser applications. It handles cross-platform transport differences, exposes a local endpoint consumed by SDKs (like Trezor Connect), and forwards structured requests so developers can focus on UX and transaction logic. Unlike wallets or custodial services, Bridge is intentionally minimal — it does not store keys, it does not sign; it simply enables safe, consistent connectivity.
Why Bridge matters
Transport inconsistencies across operating systems and browsers create friction for developers and end users. WebHID, WebUSB, and native drivers behave differently; some browsers limit USB access; some OSes require drivers or permissions. Bridge standardizes that complexity by running locally as a service that listens for device attachments and provides a unified API endpoint. By using Bridge (or relying on SDKs that detect it), applications reduce platform-specific bugs and provide a smoother pairing and signing experience.
Security model — simple and strict
The security posture is clear: private keys and seed material remain on-device at all times. Bridge acts as a conduit, not a key holder. All cryptographic operations (key derivation, signing) are executed inside the Trezor hardware. Signing requires explicit user confirmation shown on the device screen: your app should mirror human-readable transaction details so users can cross-verify what the device displays. Do not log secrets, never attempt to extract seed material, and treat the Bridge endpoint as a local-only transport.
Installation & UX guidance
Bridge is available from the official Trezor site and via platform-specific installers. On first-run it may request OS-level permissions to access USB devices; guide users with step-by-step screenshots. For browser-based apps, Trezor Connect will detect and prefer Bridge where appropriate. Your UI should detect Bridge availability and provide clear next steps: installation prompts, permission checks, and troubleshooting tips (cable check, port swap, restart Bridge). Keep messages actionable and avoid technical jargon for non-developer users.
Integration flow — developer view
Typical integration steps: initialize your SDK (Trezor Connect) → detect Bridge → enumerate devices → request public keys for address derivation → build unsigned transaction payloads on backend → send unsigned payload to device through Bridge → user reviews and approves on-device → collect signature(s) → assemble and broadcast transaction. Keep signing strictly user-initiated and present readable transaction summaries in your UI to match the on-device prompt.
Transport compatibility & fallbacks
Bridge offers a consistent fallback for environments where direct WebHID/WebUSB support is missing or restricted. Detect available transports at runtime and provide friendly guidance for fallbacks — suggest switching browsers, enabling WebHID, or installing Bridge. For desktop clients, Bridge reduces platform fragmentation and avoids per-OS quirks by exposing a reliable local endpoint that upstream SDKs can consume without duplicating transport code.
Developer best practices
Use official SDKs (Trezor Connect) whenever possible. Pin SDK and Bridge versions in your dependency matrix and maintain a compatibility table mapping client SDK versions to Bridge and firmware versions. Implement robust error handling for device disconnects, user cancellations, malformed payloads, and transport timeouts. Instrument privacy-preserving telemetry that records error types and counts but never logs private keys or seeds.
Testing & QA
Test on public testnets and use devices seeded with test-only mnemonics for end-to-end verification. Automate unit tests for transaction builders and add integration tests that exercise discovery and signing flows against a small fleet of test devices. In CI, gate hardware tests behind feature flags to ensure mainnet is never accidentally used. Keep your test devices’ firmware pinned to known-good versions to maintain reproducible regression tests.
Operational monitoring & runbooks
Monitor aggregate metrics such as Bridge detection rate, sign-operation counts, transport error rates, and firmware mismatch rates. Keep telemetry anonymized and focused on counts and error categories. Prepare runbooks for top support scenarios (device not detected, Bridge not running, permission denied) and ensure support teams can request sanitized logs that aid triage without leaking secrets.
Firmware lifecycle
Firmware updates may add features or change device behavior. Coordinate major product changes with known firmware compatibility targets and run regressions in staging. Provide in-app prompts recommending firmware updates only when necessary, and include clear recovery instructions for users to back up their recovery seed before updating.
UX & accessibility
Design pairing and signing flows with accessibility in mind: provide keyboard navigation, screen-reader friendly transcripts of on-device prompts, and clear troubleshooting guidance. Mirror the exact human-readable fields shown on the device in your UI so users (including users of assistive tech) can verify amounts, addresses, and chain information before approving transactions.
Privacy, compliance & legal notes
Bridge should never be used to collect sensitive user data. Maintain consent logs for signing events and consult counsel about custody, KYC/AML, and record retention if your product operates in regulated spaces. Clearly document what Bridge and the hardware wallet protect (private keys, signing) and which responsibilities remain with the service (broadcasting, custody policies).
Sample code (high-level)
// High-level JS using Trezor Connect (simplified)
import TrezorConnect from 'trezor-connect';
await TrezorConnect.init({ manifest: { email: 'dev@example.com', appUrl: 'https://example.com' }});
const devices = await TrezorConnect.enumerate();
const publicKey = await TrezorConnect.getPublicKey({ path: "m/84'/0'/0'/0/0" });
// Build PSBT on backend, return to client
const signed = await TrezorConnect.signTransaction({ /* psbt */ });
// Combine & broadcast
Adopting Bridge simplifies developer effort, reduces platform-specific bugs, and provides users with a reliable way to connect their Trezor device. Keep Bridge updated, test thoroughly, and present clear, matching transaction details on both app UI and device screen to preserve user trust and security.