What is Trezor Bridge?
Trezor Bridge is a lightweight local helper application that provides a stable and secure conduit between Trezor hardware wallets and desktop or browser-based applications. It standardizes communication across different operating systems and browser transport implementations (WebHID, WebUSB, native drivers), exposing a consistent local API consumed by higher-level SDKs such as Trezor Connect. Bridge's job is narrow and deliberate: forward structured messages, enumerate devices, and help manage the quirks of device discovery so developers can focus on UX and transaction logic rather than low-level plumbing.
Why Bridge matters
Different platforms expose USB and HID devices in inconsistent ways. Browsers vary in support for WebHID or WebUSB, and OS-level drivers or permissions can change behavior. Without a stable local process, applications must handle many edge cases. Bridge removes that complexity by acting as a single, local endpoint: it listens for device attachments, mediates transport details, and forwards calls to the hardware wallet. For end users this means fewer connection issues and for developers fewer platform-specific bugs.
Security model — clear separation of responsibility
The security model for Trezor + Bridge is intentionally simple: private keys and cryptographic secrets remain inside the hardware wallet at all times. Bridge is a conduit only — it does not store or modify seeds, private keys, or signed payloads. Signing operations must be confirmed on-device; the device displays human-readable details (amount, recipient, chain), and the user approves or rejects. Developers should mirror those human-readable fields in their UI so users can cross-verify what they see on the device before approving any signature.
Install & setup
Bridge installers are available from the official Trezor website and packaged for common desktop platforms. On first run, Bridge may request OS-level permissions to access USB devices — provide clear, in-app guidance and screenshots to help non-technical users enable required permissions. For web developers, Trezor Connect will detect and prefer Bridge where appropriate. Recommend users keep Bridge updated; include a simple version check inside your app to prompt upgrades when compatibility issues are detected.
Typical integration flow (developer view)
A typical integration follows these steps: initialize your SDK (for example, Trezor Connect) → detect whether Bridge is available → enumerate connected devices → request public keys for address derivation → construct unsigned transaction payloads (PSBT or chain-specific formats) on your backend → send unsigned payloads to the device through Bridge for user approval → receive signature(s) → assemble and broadcast the final transaction. Keep signing operations user-initiated and show clear transaction summaries in the app to avoid social-engineering attacks.
Transport compatibility & fallbacks
Modern browsers offer direct transports like WebHID and WebUSB, but not all environments support them uniformly. Bridge acts as a robust fallback and provides consistent behavior for older browsers or systems with restrictive permission models. At runtime, detect transport availability and guide users to the most reliable path — recommend installing Bridge, enabling WebHID, or switching to a supported browser where appropriate. Good UX here reduces support tickets dramatically.
Developer best practices
Always prefer official SDKs (Trezor Connect) rather than reimplementing transport layers. Pin SDK and Bridge versions in your dependency matrix and maintain a compatibility table mapping client SDK versions to Bridge and firmware builds. Implement robust error handling for device disconnects, user cancellations, malformed payloads, and transport timeouts. Instrument privacy-preserving telemetry (counts and error types but no secrets) to spot regressions and platform-specific issues early.
Testing & QA recommendations
Testing integrations thoroughly is essential. Use public testnets and devices seeded with test-only mnemonics for end-to-end verification. Create unit tests for transaction builders, and automate integration tests that exercise device discovery and signing flows. For critical signing logic, include hardware-in-the-loop testing in CI pipelines — gate these tests behind flags to prevent accidental mainnet operations. Keep a small fleet of test devices with pinned firmware to ensure reproducible regression checks.
Operational monitoring & support
Monitor high-level metrics such as Bridge detection rate, sign-operation counts, transport error rates, and firmware mismatch frequency. Keep telemetry anonymized and focused on counts and categories. Maintain runbooks for common support scenarios (device not found, Bridge not running, permission denied) and provide support teams with sanitized logs that aid triage without exposing secrets.
Firmware lifecycle & compatibility
Firmware updates can introduce new features or change behaviors. Coordinate product releases with firmware compatibility targets and run full regression tests in staging. Offer in-app prompts that recommend firmware updates only when necessary, and always instruct users to back up their recovery seed before performing firmware operations. Maintaining a compatibility matrix avoids unexpected breakages in production.
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 human-readable fields shown on the device in your UI so all users, including those relying on assistive technologies, can verify amounts, addresses, and chain data before approving transactions.
Privacy, compliance & legal considerations
Bridge should never be used to collect sensitive user data. Maintain consent records for signing events and consult legal counsel on custody, KYC/AML obligations, and record-keeping requirements if your product operates in regulated spaces. Be explicit in your documentation about what Bridge and the hardware wallet protect (private keys & signing) versus what your service is responsible for (broadcasting, custody policies).
Sample code (high-level)
// High-level example (JavaScript, 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 unsigned tx (PSBT) on backend; return to client
const signed = await TrezorConnect.signTransaction({ /* psbt */ });
// Combine signatures and broadcast
Adopting Trezor Bridge as your transport layer reduces platform friction, centralizes debugging, and gives users a reliable, consistent way to connect their hardware wallets. Keep SDKs and Bridge versions pinned during releases, test across firmware variants, and present clear transaction details in both app UI and device screens to preserve user trust and security.