CleverGet is currently one of the most stable desktop solutions for 9Anime. It is specifically designed to bypass the site's anti-downloading scripts. Supports up to 4K and 8K UHD.
Play the anime episode on 9Anime, and the extension icon will light up when it detects the video stream. Click it to choose your preferred resolution (e.g., 720p or 1080p).
Once installed, an "IDM Download this video" panel appears above the player. You can also use the 9anime-downloader script on GitHub to grab all episode links at once and paste them into IDM's batch download feature.
If you don't want to install software, TubeOffline is a reliable web-based service. Simply paste the 9Anime URL, and it will generate a download link for you.
Available for and Firefox , Video DownloadHelper is a lightweight alternative to standalone software.