Seamless, secure middleware connecting your Trezor device and your web interface
The Trezor Bridge is a fundamental component in the Trezor ecosystem, acting as a bridge (middleware) between your Trezor hardware wallet and web applications (or local apps) that need to communicate with it. It facilitates secure, transparent communication channels, ensuring that your private keys remain isolated within the hardware while allowing browser-based dApps or wallets to interact safely.
Before its inception, communication with the Trezor device was typically handled via direct USB or via older interfaces (like Trezor Chrome extension). The Bridge was introduced to standardize and streamline these connections, minimize friction, and reduce the dependence on browser-specific extensions. Users no longer need to install a browser plugin; instead, the Bridge runs as a background service.
In practical terms, when you connect your Trezor device and open a web wallet interface, the site detects the Bridge (if installed), communicates via local HTTP or WebSocket endpoints, and relays commands (such as “get addresses,” “sign transaction,” etc.). The hardware wallet performs operations internally, and only signed data is returned to the calling application.
The internal architecture of Trezor Bridge consists of several modular parts: the Bridge daemon, the transport layer, an RPC (Remote Procedure Call) interface, and device-specific adapters. The daemon runs locally on your machine, listening on a loopback address (e.g. `127.0.0.1`) at a particular port. It authenticates incoming requests only from registered origins, mitigating unauthorized access.
The transport layer abstracts low-level USB communication, handling packetization, framing, and device enumeration. The RPC interface maps high‑level commands (like `GetPublicKey`, `SignTransaction`) to the transport, marshals parameters, and returns results. Adapters ensure compatibility across different Trezor models (e.g. Model T, One) and firmware versions.
A security-oriented design ensures that only local applications on your machine can reach the Bridge. Remote or networked access is blocked by default. The Bridge also checks digital signatures of communicating applications to guard against spoofing. Everything is built with defense in depth.
To begin, download the Bridge installer from the official Trezor website. The installer is available for Windows, macOS, and Linux. During installation, a local background process is installed, and necessary firewall permissions are configured (if needed).
Once installed, reconnect your Trezor hardware. Visit a compatible web wallet interface (for example, the official Trezor Web Wallet or a third‑party wallet supporting Trezor). The site should prompt detection of the Bridge. If not, the site may guide you to “Install Bridge,” which links to the installer.
After connection, you can interact with your wallet: retrieve account addresses, view balances, create transactions, and ask the device to sign them. Each transaction must be manually confirmed on the physical device, reinforcing security.
For developers, the Bridge provides an API specification. Web apps can send JSON‑RPC commands via HTTP POST to the local Bridge endpoint. Typical commands include `enumerate`, `get_features`, `apply_settings`, `sign_tx`, `sign_message`, etc. It’s vital that apps validate the device response and not bypass user confirmation.
Because Trezor Bridge is a critical piece connecting web apps and hardware, security measures are integral. Here are recommended best practices:
Origin whitelisting: The Bridge maintains a whitelist of allowed web origins. When a new site attempts to connect, you’ll see a prompt to allow or deny access. Only accept trustworthy domains.
Firmware validation: Always ensure your Trezor device runs the latest official firmware. The Bridge and device firmware collaborate — new communication protocols or validations may depend on matching versions.
Network isolation: The Bridge operates over loopback (localhost) interfaces, never exposing interfaces to remote networks. Avoid configurations that map local services externally, which could introduce vulnerability.
Manual confirmations: Even if a malicious site attempts to craft a transaction, it cannot bypass your physical confirmation. Always scrutinize the address, amount, and fee on the device screen.
Backup & recovery: If your Bridge installation fails or your machine is replaced, ensure your recovery seed is securely stored. You can reinstall Bridge later and regain access to the hardware wallet.
Answer: The Trezor Bridge is a local background service (middleware) that allows web applications and local wallets to communicate securely with your Trezor hardware wallet. It enables transactions, key retrievals, and device configuration without exposing private keys.
Answer: Yes, for most users you install it manually via the official Trezor website. The installer sets up the Bridge daemon, necessary system permissions, and firewall rules. Once installed, most compatible web wallets detect it automatically.
Answer: No. The Bridge enforces an origin whitelist. When a new domain requests access, the user will be prompted to allow or deny. Only allowed origins can send RPC commands to Bridge.
Answer: No. The Bridge communicates over local loopback interfaces (e.g. `127.0.0.1`) and does not expose endpoints externally. It never sends your private keys or secrets over the network.
Answer: Incompatibilities can lead to failed operations or communication errors. Always update both Bridge and device firmware to compatible versions as recommended by Trezor. If issues arise, reinstall Bridge or roll back to stable firmware versions.
RPC (Remote Procedure Call): A protocol for requesting actions (like “sign transaction”) from the Bridge, which then relays to the hardware device.
Daemon / service: A background program running invisibly that listens for communication requests (in this case, the Bridge service).
Localhost / loopback: Network interfaces (e.g. `127.0.0.1`) that only applications on the same machine can access — used by Bridge to isolate traffic.
Origin: The domain (scheme + host + port) from which a web page is served. Bridge verifies origin to resist unauthorized access.
Firmware handshake: During communication, the Bridge and the Trezor device exchange feature messages and versioning information to ensure compatibility and integrity.