Save a compatible video from Safari on iPhone
In Safari, accept the download prompt and locate the completed item in Downloads in the Files app. From Files, use Share and choose Save Video only when iOS recognizes the file as compatible with Photos. Some containers or codecs remain available in Files but cannot be added directly to Camera Roll. Resolution depends on the source, and a larger 1080p or 4K file needs more storage and transfer time. Keep Safari available until the download starts and respect iOS storage permissions.
Safari on iPhone uses iOS's normal download handling, so a third-party downloader app is not needed. After YTMetadata resolves the public link, choose an MP4 representation that the source actually provides. HD video may arrive as separate DASH video and AAC audio tracks that the service muxes before returning the file. MP4 is a container, not a codec guarantee; H.264 video with AAC audio is generally the safest choice for Apple playback, while support for newer codecs varies by iOS version and app.