Executive summary
Trezor Bridge is the secure, lightweight local helper application that enables desktop and web applications to interact with Trezor hardware wallets. It abstracts transport differences across platforms and browsers (WebHID, WebUSB, native drivers) and exposes a consistent, local API consumed by higher-level SDKs such as Trezor Connect. By using Bridge, developers avoid brittle low-level plumbing and users gain a smoother, more reliable experience for discovery, pairing, and signing.
Why Bridge exists
Different operating systems and browsers expose device transports inconsistently. Bridge standardizes the local endpoint so applications only need to support a single path to reach devices. It runs as a small background process, listens for device attachments, and mediates messages between the Trezor device and your app. Importantly, Bridge is not a wallet: it does not hold keys or modify transactions — it simply forwards requests and responses while the hardware wallet performs cryptographic operations.
Security model
Security is simple and strict: private keys and sensitive seed material remain inside the hardware wallet at all times. Bridge only forwards structured API messages. Signing operations require explicit on-device confirmation by the user; the device displays human-readable data that should match your app's UI. Always design your UI to display the same human-readable details shown on the device (amounts, recipient, chain) and instruct users to verify them before approving a signature.
Install & setup
Bridge is available from the official Trezor website and via platform-specific installers where appropriate. When users install Bridge, it may request OS-level permissions to access USB devices; ensure your application guides users through these steps with clear screenshots or tooltips. For browser environments, Trezor Connect will detect Bridge automatically and use it as a transport when needed. Encourage users to keep Bridge updated and include a version check in your app that surfaces an upgrade prompt when compatibility issues arise.
Typical integration flow
A common flow looks like: initialize Trezor Connect (or your SDK) → detect Bridge availability → enumerate devices → request public key(s) for addresses → build unsigned transaction (PSBT or chain-specific format) on the backend → send unsigned payload to the device through Bridge → user reviews and approves on-device → receive signature(s) → assemble final transaction and broadcast to network. Keep heavy cryptographic work server-side when possible; keep signing tied to user action.
Developer best practices
Use official SDKs (Trezor Connect) and avoid reimplementing device transports unless you have a strong reason. Pin SDK versions in your dependencies and maintain a compatibility matrix that maps SDK versions to Bridge and firmware versions. Implement defensive error handling: handle device disconnects, user cancellations, malformed payloads, and transport timeouts gracefully. Instrument your integration with privacy-preserving telemetry that captures failure types but never logs keys or seeds.
Testing & QA
Testflows should exercise both happy-path and edge-case behaviors. Use public testnets and devices seeded with test-only mnemonics for E2E tests. Include unit tests for your transaction builders and CI integration tests that interact with a small fleet of test devices. In CI, gate hardware tests behind flags to prevent accidental mainnet operations. Maintain pinned firmware versions on test devices for reproducible regression results.
Transport compatibility & fallbacks
Modern browsers support WebHID and WebUSB; Bridge provides a consistent fallback especially for older browsers or OS configurations where direct transports are not available. Detect transports at runtime and offer user-friendly guidance when fallbacks are required—show clear instructions for installing Bridge, enabling WebHID, or switching to a supported browser. Ensuring users have the right cable and avoiding USB hubs solves many connectivity problems.
UX & accessibility
A good UX foresees common issues: include step-by-step pairing screens, progress indicators while the device awaits confirmation, and readable transcripts of what the device displays for screen-readers. Provide keyboard-accessible flows and concise troubleshooting tips (check cable, restart Bridge, verify firmware). When asking users to confirm transactions, mirror the device display in your UI so users can cross-verify quickly.
Operational monitoring
Monitor high-level metrics: Bridge detection rate, sign-operation counts, transport error rates, and firmware-mismatch occurrences. Use anonymized counters and error types — do not collect sensitive details. Maintain runbooks for common support scenarios (device not found, Bridge not running, permission denied) and provide support teams with sanitized logs that include only metadata necessary to triage.
Firmware lifecycle & compatibility
Firmware updates may change device behavior or expose new features. Coordinate app releases with known firmware compatibility targets and run full regression tests in staging. Offer in-app prompts that recommend firmware updates only when necessary, and provide clear guidance for users to back up their recovery seed and follow update instructions carefully.
Privacy, compliance & legal
Bridge acts as a conduit and should never be a vector for collecting sensitive user secrets. Maintain consent logs for signing events and design audit trails that preserve privacy. If your product operates in regulated verticals, consult legal counsel about custody, KYC/AML, and record retention. For custodial features, clearly document the limitations of what on-device signing protects and what your service is responsible for.
Sample code (high-level)
// High-level JS using Trezor Connect
import TrezorConnect from 'trezor-connect';
await TrezorConnect.init({ manifest: { email: 'dev@example.com', appUrl: 'https://example.com' }});
const devices = await TrezorConnect.enumerate();
const pubkey = await TrezorConnect.getPublicKey({ path: "m/84'/0'/0'/0/0" });
// Build PSBT on backend, return psbt
const signed = await TrezorConnect.signTransaction({ /* psbt */ });
// Combine signatures and broadcast
By adopting Bridge as your transport layer, you minimize cross-platform differences, reduce support overhead, and help users interact with hardware wallets reliably. Bridge is a mechanical piece of infrastructure — small, well-scoped, and focused on forwarding requests to the single source of truth: the hardware wallet itself.