What is Trezor Bridge?

Trezor Bridge is (or was) a small background service (daemon) developed by SatoshiLabs for enabling secure communication between a Trezor hardware wallet (such as Model One, Model T, Safe 3, etc.) and browser-based interfaces (or other software) running on your computer. In essence, it acts as a translator or “bridge” between the USB protocols used by the device and web APIs that want to talk to it.

Because browser-native USB support is limited or inconsistent (especially historically), the Bridge handled detection, message passing, and encryption between your Trezor device and the “outside” world (web apps, wallet UIs, etc.) without exposing sensitive keys to the computer or browser itself.

When you run a web wallet that supports Trezor, that web app would communicate (usually via HTTP requests to localhost) with the Bridge process, which would forward those commands to the hardware wallet, let you confirm actions (e.g. signing a transaction) on the device, and pass responses back. The private keys never leave the hardware — the Bridge is just a conduit.

Why Was Trezor Bridge Used?

1. Compatibility across browsers

Not all browsers supported direct hardware access. For example, some browsers didn’t support WebUSB or WebHID (APIs that allow web pages to talk to USB devices). The Bridge provided a universal, browser-agnostic way to connect your Trezor to web apps or wallet interfaces without relying on browser extensions.

2. Avoiding browser extensions / plugins

Using browser extensions or plugins brings additional security risks (malicious updates, injection attacks, etc.). Bridge situates the sensitive operations in a background service outside the browser, reducing the attack surface.

3. Seamless device detection & communication

Bridge would run quietly in the background, auto-detect the Trezor hardware, and manage communication, making the user experience smoother (e.g. no need to install USB drivers manually, no need for browser plug-ins to be updated constantly).

4. Legacy / third-party integration

Bridge enabled third-party wallets (like MyEtherWallet, MetaMask, etc.) to integrate Trezor support, even if they weren’t designed from the ground up to talk to hardware wallets.

Deprecation & Evolution: Bridge Is Being Phased Out

It's important to understand that the standalone Trezor Bridge has been deprecated and is being removed in favor of built-in or more modern connection methods. Trezor+1

Trezor’s official documentation now recommends that users uninstall the standalone Bridge and instead rely on Trezor Suite (desktop or web) which includes the connectivity layer internally. Trezor

In particular: