Essential Component for Hardware Security
The secure communication layer that ensures seamless, private, and cryptographic interaction between your browser-based wallet interface and your physical Trezor device. This is the bedrock of non-custodial self-sovereignty.
Trezor Bridge is a small, standalone application that runs on your computer's operating system (Windows, macOS, or Linux). Its sole and vital purpose is to act as a secure intermediary between the Trezor Wallet web application (running in your browser) and the USB-connected Trezor hardware device.
Without the Bridge, the modern, user-friendly web interface cannot securely detect, communicate with, or authorize transactions via your hardware wallet. It is the crucial link in the chain of trust.
Operating systems often restrict direct, low-level access to USB hardware for security reasons. The Bridge sidesteps this limitation by running locally and providing an authorized WebSocket interface (usually on `localhost:21325`) that the Trezor Web Wallet can communicate with. This local, cryptographically verified connection ensures that only the Trezor service can talk to the device.
**Auto-detection:** The Bridge constantly monitors USB ports, instantly recognizing and connecting to your Trezor Model One or Trezor Model T when plugged in.
**Low Resource Usage:** Designed to be lightweight and unobtrusive, it runs silently in the background without impacting system performance.
**Cross-Platform Support:** Ensures a consistent experience regardless of the user's operating system environment.
Web browsers are intentionally sandbox-constrained environments. They are prevented from arbitrary access to local files and hardware ports like USB. The Bridge is a privileged, locally installed daemon that is required to communicate with the Trezor device at the hardware level, granting the necessary permissions securely and locally.
Communication between the browser and the Bridge is secured using WebSockets and is protected by Transport Layer Security (TLS). Critically, it uses self-signed certificates with a known public key, ensuring that only a genuine Trezor Wallet application can establish a connection with the local Bridge service, preventing Man-in-the-Middle (MITM) attacks.
While some wallets rely on potentially intrusive browser extensions (which can read all your web activity), the Bridge runs outside the browser context. This minimizes the attack surface and ensures that the core security interaction is delegated to a specialized, secure, and minimal local application.
The entire communication flow is structured to protect your secrets. When you initiate a transaction in the web wallet, the application sends a request to the local Bridge. The Bridge relays this command over USB to the Trezor device. The device processes the request internally (signing the transaction using your private key, which *never* leaves the device), and returns the signed transaction data back to the Bridge, which then passes it back to the web wallet for broadcast. The Bridge never sees your private key or recovery seed—it is purely a secure data pipe.
The entire codebase for Trezor Bridge is open source, allowing community and professional security researchers to audit its integrity and ensure it performs exactly as advertised.
Native installers are provided for Windows, macOS, and Linux (including various distributions), guaranteeing near-universal compatibility for users worldwide.
The Bridge client includes a robust automatic update mechanism, ensuring users always run the latest version with critical security patches and feature enhancements.
Optimized for speed, the communication protocol ensures near-instantaneous response times between the web interface and the physical Trezor device for smooth transaction signing.
**Status Check:** You can usually verify the Bridge's operational status by checking the services running on your computer. It is registered as a background service or daemon named `Trezor Bridge`.
**Port Verification:** The communication happens over a localhost WebSocket connection (default port 21325). Firewall rules rarely interfere, as the traffic remains within your local machine.
**If Detection Fails:** Ensure the USB cable is functional and correctly plugged into both the device and the computer. Restarting the Bridge service or rebooting the computer usually resolves transient issues.
It is the invisible, yet indispensable, component that bridges the security of the hardware layer with the accessibility of the web, upholding the core principles of decentralized finance and self-sovereignty.
The underlying protocol and Bridge architecture are utilized by third-party cryptocurrency wallets, exchanges, and services, demonstrating its robust design and wide-ranging utility across the entire crypto ecosystem. Developers can leverage the Trezor Connect SDK, which seamlessly integrates with the Bridge, to add hardware wallet support to their own applications.