SignBridge is a free Chrome extension designed for secure PDF document signing using hardware security modules (HSM), smartcards, and USB tokens via the PKCS#11 standard. It acts as a bridge between web applications and a native host application installed locally on your computer. When signing is requested, the extension communicates with the native host to execute the signing operation, ensuring that private keys remain secure and within the hardware device itself.

Key features include support for both single and batch signing workflows, customizable signature appearances, and compliance with PAdES B-B and B-T signature profiles. The extension guarantees privacy by not collecting or storing user data, and all cryptographic processes occur locally. Developers can easily integrate SignBridge into their web applications using a lightweight JavaScript SDK, making it a versatile tool for enhancing document security.