StreamStitch от Jonah Kowall

StreamStitch detects HLS, DASH, direct video, and direct audio while you browse, then saves media you are authorized to download. Processing, temporary media, settings, credentials, and history stay inside Firefox. Compatible media is remuxed losslessly, with MKV fallback when MP4 is not suitable.

StreamStitch does not bypass DRM, recover unavailable keys, support YouTube, transcode media, load remote code, use analytics, or send media and browsing data to a StreamStitch service.