MP4 (MPEG-4 Part 14) is a multimedia container format that can hold video, audio, subtitles, and metadata. It's the most widely supported video format on the internet, compatible with every major device, browser, and platform. Importantly, MP4 is a container — the actual video compression is handled by a codec stored inside (typically H.264, but also H.265, VP9, or AV1).
MP4 with H.264 video and AAC audio is the universal standard for sharing videos: it plays natively on iPhone, Android, Windows, Mac, Linux, Chrome, Firefox, Safari, Edge, VLC, and every other video player. H.265 MP4 offers better compression but has slightly less universal support (older devices may require hardware decoder support).
For online sharing (WhatsApp, email, social media), MP4 with H.264 at appropriate bitrate is always the right choice. For archiving, H.265 MP4 offers 40% better compression at the same quality. FileCurve's video compressor outputs MP4 files using H.264 encoding, optimized for web and mobile sharing.