Overview — What is Trezor Bridge?
Short definition
Trezor Bridge is a lightweight, vendor-supplied application that acts as a secure bridge between a user's web browser and a Trezor hardware wallet connected to the computer. It exposes a local, browser-facing API that web pages (wallet apps, exchange integrations, dapps) use to communicate with the hardware device using standard web APIs and a small transport protocol that runs over localhost. Bridge abstracts complicated USB/HID interactions so browsers can interact with hardware wallets without requiring browser-specific native integrations.
Key points
- Runs as a native background process on the user's machine.
- Provides web applications with a consistent interface to the device.
- Handles platform and browser differences (Windows, macOS, Linux).
Speaker note: keep the intro concise and emphasize it is a compatibility layer not a compromise on security.
Why Bridge? Problems it solves
Challenges without Bridge
Prior to Bridge, web apps struggled to access hardware wallets consistently. Browsers have limited direct USB access (and historically inconsistent APIs), OS drivers differ, and cross-platform device discovery can be fragile. Without a standard connector, each wallet provider or browser extension must implement platform-dependent code, leading to fragmentation.
Bridge solves:
- Device discovery across operating systems.
- Permission model and secure channel for browser-to-device calls.
- Versioning and update control independent of browsers.
Speaker note: use a short demo animation or diagram when presenting — visually showing the problem and the Bridge in the middle simplifies comprehension.
Architecture — How Bridge fits in the stack
Layers
The Bridge sits between three layers: the web application (frontend), the host OS (with USB/HID drivers), and the Trezor device (hardware wallet). Internally Bridge exposes an HTTP/HTTPS-like local endpoint, offering JSON-RPC style or REST endpoints that forward requests to the device over the native device transport. It implements authentication tokens, CORS rules, and optional TLS for localhost.
Components
- Local server: listens on localhost and accepts signed requests from allowed origins.
- Transport manager: enumerates devices, opens HID/USB endpoints, and queues messages.
- Updater: checks and installs Bridge updates with user consent.
Speaker note: show a simple diagram. Emphasize that the device always signs transactions locally — Bridge only forwards, not signs.
Installation & Update Flow
Installing Bridge
Users download Bridge installer for their OS (Windows MSI, macOS PKG/dmg, or Linux packages). The installer registers a small background service and may prompt for permission to access USB devices. Once installed, Bridge auto-runs and exposes a localhost endpoint. Many wallet web apps include a "Detect Trezor" button that will prompt the user to install Bridge if it's missing — the site links to the official download.
Update model
Bridge has an update component that can check for new releases. Updates should be signed and delivered via an authenticated channel; user consent is required for system-level changes. Administrators in enterprise environments can manage Bridge via package managers.
Speaker note: mention where to download (official vendor site) and recommend verifying checksums and signatures when distributing in sensitive environments.
Browser Compatibility & Native APIs
Browsers landscape
Modern browsers increasingly support WebUSB and WebHID APIs, but availability and user permission flows differ. Bridge fills gaps by providing a consistent local HTTP endpoint that all browsers can call without relying on experimental browser features. This increases compatibility for web wallets and dapps that need a dependable transport to hardware wallets.
When to use Bridge vs native APIs
- Use native WebUSB/WebHID for users who prefer direct browser integrations and if available.
- Use Bridge to support older browsers, cross-browser consistency, and platforms where WebUSB is blocked or incomplete.
Speaker note: provide comparative table live during demo: WebUSB vs WebHID vs Bridge — pros and cons.
Security Model & Threat Analysis
Security first
Bridge is designed to minimize risk: it never has access to user PINs or private keys; the Trezor device performs all key operations and signing. Bridge only forwards commands and receives structured responses. The security model rests on three pillars: device security (secure chip and firmware), local endpoint security (restricting origins and user confirmations), and platform integrity (OS-level protections).
Main threats considered
- Malicious local applications attempting to call Bridge — mitigated via origin checks, user prompts, and tokens.
- Man-in-the-middle between browser and Bridge — mitigated by localhost-only endpoints and optional TLS with pinned certificates.
- Compromised OS — if the OS is compromised, hardware wallets still protect private keys but transaction context may be manipulated; always verify details on device screen.
Speaker note: stress the single golden rule — always verify transaction details on the Trezor device display before confirming.
Developer Integration — API & Examples
How web apps connect
Integration is typically straightforward: the web app attempts to open a connection to the Bridge localhost endpoint using a known port or discovery method. After handshake and origin validation, the app sends JSON-formatted commands (get public key, sign message, etc.). Libraries and SDKs abstract the low-level details; developers should prefer official SDKs to ensure compatibility and correct permission flows.
Best practice snippets
// pseudo-code example
const client = new TrezorBridgeClient({bridgeUrl: "http://localhost:21325"});
await client.handshake();
const pk = await client.getPublicKey({path:"m/44'/0'/0'/0/0"});
await client.signTransaction({inputs, outputs});
Speaker note: mention official SDK docs and sandbox examples. Highlight robust error handling and timeouts in code.
User Experience & Troubleshooting
Common UX flows
On first use, users are prompted to install Bridge. After installation, the wallet app should detect the device and show clear, stepwise instructions (connect device, unlock device, confirm on device). Typical issues include port conflicts, device drivers missing, or firewall restrictions. A guided troubleshooting section in the app reduces support tickets substantially.
Common troubleshooting checklist
- Confirm Bridge is running (system tray / menu bar indicator).
- Make sure the hardware device is unlocked and the right app on device is selected.
- Temporarily disable interfering app (some antivirus or USB managers).
- Reinstall Bridge using official installer and verify signatures if available.
Speaker note: present live demo with a checklist and ask attendees to follow one by one during a hands-on session.
Best Practices & Policies
For users
- Only download Bridge from official distribution channels.
- Keep device firmware and Bridge updated.
- Always verify transaction data on the device display, never only in the browser.
For integrators
- Use official SDKs; avoid building custom low-level drivers unless necessary.
- Implement clear, security-focused permission prompts and provenance UI in the website.
- Provide a visible and accessible troubleshooting/help link in the integration UI.
Speaker note: include short list of compliance and logging guidelines for enterprise deployments.
Summary & Next Steps
Takeaways
Trezor Bridge is a pragmatic compatibility layer that enables web apps to interact with hardware wallets in a secure and consistent manner. It preserves hardware-level security by ensuring that signing and key management remain on the device while solving cross-browser and cross-platform connectivity issues. For developers and product teams, Bridge reduces complexity and improves user reliability. For users, Bridge simplifies hardware-wallet usage and increases interoperability across services.
Recommended next steps
- For product teams: prototype Bridge integration using official SDKs and run a small user test.
- For security teams: audit end-to-end flows and observe how user confirmations are shown on device.
- For users: install Bridge from vendor site and practice sending small transactions to verify your setup.