IDM is the undisputed king. When you play a video on 9anime, IDM detects the stream and pops up a "Download this video" button.
9anime operates without licensing agreements from Japanese studios (like Toei, MAPPA, or Kyoto Animation). While streaming might exist in a gray area depending on your country, a copy of a copyrighted anime without paying for it is explicitly copyright infringement. 9anime mp4 downloader
This is the successor to youtube-dl. It bypasses most encryption on streaming sites. IDM is the undisputed king