Native phone playback; supports R-18 filters if you are logged in. Cons: iOS users have fewer options due to App Store restrictions.
Excellent for fine-tuning animation speed; works on Android/iPhone browsers. Cons: Occasional server overload during peak hours. Ugoira Downloader
Technically, an Ugoira is not a video file (like MP4) nor a standard animated GIF. Instead, Pixiv developed a proprietary format consisting of: Native phone playback; supports R-18 filters if you