How to download?
For Computer: Right click the "Download" button, then click "Save link as..." to save the video or audio files.
For smart phone/tablet: Touch and hold the "Download" button, then tap "Download link" to download the video/audio files.
For HD videos (>=1080P): For HD videos with resolution greater than 1080P (1080P, 2K, 4K, 6K & 8K) especially from Youtube, detailed tutorials: https://distillvideo.com/page/how-to-download-youtube-hd-video-without-losing-any-quality
Or get this Video Processing Software to batch download 4K UHD/HD videos, music, playlist; record screen, webcam; convert, compress, cut, trim, merge, crop and process your downloaded content.
Download Failed - Network error : In most cases, it means the server blocked your IP, you should use a VPN to bypass such restriction.
Alternative method - use a desktop free video downloader to obtain online videos, which enables proxy settings and frees you from restriction in downloading.