Video files have two parts: a container (the file format — MP4, MOV, MKV) and a codec (the compression method used inside it — H.264, H.265). The container is what you see in the file name; the codec is what determines quality, size and compatibility. Understanding both makes it much easier to know which format to use and why conversion sometimes fixes playback problems.
The Four Main Formats
MP4 (.mp4)
The default format for almost everything — phones, tablets, computers, browsers, streaming platforms, messaging apps and editing software all support it.
- Best for: sharing, uploading, streaming, WhatsApp, social media, everything.
- Codec inside: usually H.264 (most compatible) or H.265 (smaller files, needs more modern hardware).
MOV (.mov)
Apple's native format, created with iPhone and Mac. Very high quality, but limited support outside Apple devices and professional editing software.
- Best for: editing on a Mac; when the recipient specifically uses Apple software.
- Problem: many Android phones, Windows apps, websites and streaming platforms don't support it directly.
- Fix: convert to MP4 with MOV to MP4.
MKV (.mkv)
A flexible container that can hold multiple audio tracks, subtitles and chapters in one file. Common for films and downloaded content.
- Best for: storing films with multiple language tracks and subtitles.
- Problem: many phones, smart TVs and streaming platforms don't support MKV without extra software or apps.
- Fix: convert to MP4 with MKV to MP4.
AVI (.avi)
An older Windows format from the 1990s. Still common but uses older, larger codecs and is not widely supported on mobile or web.
- Best for: playing back old recorded content where you have no other option.
- Problem: large file sizes, poor mobile support, not accepted by most upload platforms.
- Fix: convert to MP4 with AVI to MP4.
Format Comparison Table
| Format | Universal playback | File size | Subtitles | Best codec |
|---|---|---|---|---|
| MP4 | ✓ Excellent | Small-medium | Basic | H.264 or H.265 |
| MOV | Limited (Apple) | Medium-large | Yes | ProRes, H.264 |
| MKV | Limited (needs app) | Varies | Excellent | Any |
| AVI | Moderate | Often large | Limited | Older codecs |
Why MP4 Won
MP4 became the universal standard because it balances quality, compression and compatibility — a 1080p video at a reasonable bitrate fits in a manageable file that virtually everything can play. The other formats still exist because each serves a specific context, but for everyday use, sharing, and uploading, MP4 is almost always the right choice.
Converting to MP4
- MOV → MP4: MOV to MP4
- MKV → MP4: MKV to MP4
- AVI → MP4: AVI to MP4
These conversions preserve the content and produce a file that plays on phones, TVs and virtually any platform. For the underlying technical details — codecs, bitrate, resolution — see what is a video codec and what is video bitrate.
