The Stream Detector by 54ac

This is a Firefox addon which provides an easy way to keep track of URLs to playlists and subtitles used by Apple HLS, Adobe HDS, MPEG-DASH, and Microsoft Smooth Streaming streams as well as download video/audio files directly and monitor any other file extensions and Content-Type headers.

Copy URLs by clicking their filenames in the addon's popup menu (accessed by clicking on the toolbar icon). URLs can either be copied as they are or transformed into readymade yt-dlp (recommended), FFmpeg, Streamlink, hlsdl or N_m3u8DL-CLI commands, including the User-Agent, Cookie, and Referer headers. The chosen tool then downloads the stream into a single file until it is finished or stopped. Use the addon's options page to customize your experience and e.g. download media files directly.

Note that websites such as YouTube, Vimeo, Facebook, etc. are very likely to use proprietary technologies which are not supported by this addon. When it comes to such "mainstream" services, it's better to use the tools (e.g. youtube-dl/yt-dlp) directly.