Browser extension for KeePassXC with Native Messaging.
Please see this document for instructions how to configure KeePassXC in order to connect the database correctly.
How it works
There are two methods which you can use KeePassXC-Browser to connect to KeePassXC:
KeePassXC-Browser communicates with KeePassXC through keepassxc-proxy. The proxy handles listening to STDIN/STDOUT and transfers these messages through Unix domain sockets / named pipes to KeePassXC. This means KeePassXC can be used and started normally without inteference from Native Messaging API. KeePassXC-Browser starts only the proxy application and there's no risk of shutting down KeePassXC or losing any unsaved changes. You don't need to install keepassxc-proxy separately. It is included in the latest KeePassXC fork. Alternatively you can use keepassxc-proxy-rust as a proxy if you prefer a non-Qt solution. There's also Python and C++ versions available at keepassxc-proxy.
KeePassXC-Browser communicates directly with KeePassXC via stdin/stdout. Using native messaging directly is a more secure as it ensures the traffic between KeePassXC and KeePassXC-Browser is direct. This method launches KeePassXC every time you start the browser and closes when you exit. This can cause unsaved changes not to be saved. If you use this method it's important to enable
Automatically save after every changefrom KeePassXC's preferences. Because this option is not preferred as default it's good to test this feature with your OS and ensure KeePassXC asks to confirm any unsaved changes before exit.
The details about the messaging protocol used with the browser extension and KeePassXC can be found here.