: You can open the Chrome Console (F12 or Ctrl+Shift+J) and paste a snippet that identifies the hd_src or sd_src within the page's metadata.
For large-scale projects, developers often use API wrappers. Decoding facebook's blob video url - Stack Overflow script download facebook video
: Many Facebook videos separate audio and video streams for HD quality. Scripts like the one found on the TufayelLUS GitHub repository use FFmpeg to download these separate tracks and merge them into a single high-quality file. : You can open the Chrome Console (F12