Firefox has supported screen capture since version 33 using the mediaSource constraint in the mediaDevices API, which allows developers to access a stream of the user's screen. However, before Firefox version 52, this capability was only available on sites that were added to an allow list. Since Firefox version 52, this feature is available to all sites served over HTTPS, but requires a self-signed TLS certificate or ngrok for local testing due to security restrictions imposed by Firefox. The code for implementing screen capture in Firefox involves using the `navigator.mediaDevices.getUserMedia` method with the `video` object and specifying the desired media source, such as "screen", "window", or "application".