The Firefox remote agent is a low-level debugging interface based on the CDP protocol. With it, you can inspect the state and control execution of documents running in web content, instrument Gecko in interesting ways, simulate user interaction for automation purposes, and debug JavaScript execution. This component provides an experimental and partial implementation of a remote devtools interface using the CDP protocol and transport layer. See https://firefox-source-docs.mozilla.org/remote/ for documentation. The remote agent is not by default included in Firefox builds. To build it, put this in your mozconfig: ac_add_options --enable-cdp This exposes a --remote-debugger flag you can use to start the remote agent: % ./mach run --setpref "browser.fission.simulate=true" -- --remote-debugger