Video Formats Explained: MP4, MKV, AVI, MOV, WebM & More
Published February 28, 2026 · 11 min read
Video files are more complex than images or audio because they combine multiple streams — video, audio, subtitles, and metadata — inside a "container." Understanding the difference between containers and codecs is the key to navigating video formats.
Containers vs. Codecs
A container (MP4, MKV, AVI) is the file format — the wrapper that holds everything together. A codec (H.264, H.265, VP9) is the compression algorithm that encodes the actual video data inside the container. The same codec can live inside different containers. An MP4 file might contain H.264 video, while an MKV file might also contain H.264 video — same video quality, different packaging.
MP4 (MPEG-4 Part 14)
The universal standard. MP4 is supported by every browser, every phone, every TV, every video player, and every social media platform. It typically contains H.264 or H.265 video with AAC audio. If you're unsure which format to use, MP4 with H.264 is always the safe choice.
Limitations: MP4 doesn't support many subtitle formats or multiple audio tracks as elegantly as MKV.
MKV (Matroska)
The power user's container. MKV can hold virtually unlimited video, audio, and subtitle tracks in a single file. It supports every codec ever created. MKV is the format of choice for archiving movies (multiple audio tracks, multiple subtitle languages, chapter markers). The downside: many devices and platforms don't play MKV natively — you may need to convert to MP4 for compatibility.
AVI (Audio Video Interleave)
Microsoft's legacy container from 1992. AVI is technically obsolete — it doesn't support modern codecs well, has limited metadata support, and produces larger files. However, you'll still encounter AVI files from older cameras, screen recorders, and archived content. When you receive an AVI file, converting to MP4 is almost always the right move.
MOV (QuickTime)
Apple's container format. MOV files from iPhones and Final Cut Pro are essentially MP4 files with some Apple-specific extensions. MOV works great within the Apple ecosystem but can cause playback issues on Windows and Android. For sharing, convert MOV to MP4.
WebM
Google's open-source web video format, based on the Matroska container with VP8/VP9/AV1 video and Vorbis/Opus audio. WebM is optimized for web streaming and is used extensively by YouTube. All modern browsers support WebM playback. It offers excellent compression but limited support outside of web contexts.
Video Codec Quick Guide
| Codec | Compression | Quality | Best For |
|---|---|---|---|
| H.264 (AVC) | Good | Great | Maximum compatibility |
| H.265 (HEVC) | ~40% better | Excellent | 4K streaming, storage |
| VP9 | ~30% better | Excellent | YouTube, web |
| AV1 | ~50% better | Superior | Future of web video |
Which Format Should You Use?
- Sharing/uploading: MP4 with H.264 — works everywhere
- Archiving: MKV with H.265 — best compression, keeps all tracks
- Web embedding: WebM with VP9 or MP4 with H.264
- Editing: MOV/MP4 with ProRes or DNxHR (editing codecs)