Video Formats Explained: MP4, MOV, WebM, MKV
By Joe Crozier · December 14, 2024
Choosing the right video format matters. The wrong choice can mean compatibility issues, bloated file sizes, or unnecessary quality loss. This guide covers everything you need to know about the most common video formats.
Containers vs. Codecs
Before diving into specific formats, understand these two concepts:
Container — The file format that holds video, audio, and metadata together. This is what you see as the file extension: .mp4, .mov, .mkv.
Codec — The compression algorithm that encodes and decodes the actual video data. Common codecs include H.264, H.265 (HEVC), VP9, and AV1.
A single container can support multiple codecs. An MP4 file might contain H.264 or H.265 video. Compatibility depends on both the container and the codec inside.
MP4
The universal standard
MP4 (MPEG-4 Part 14) is the most widely supported video format. Developed by the Moving Picture Experts Group, it has become the default choice for digital video across platforms.
Strengths
- • Plays on virtually every device
- • Excellent compression efficiency
- • Native support on all social platforms
- • Good balance of quality and file size
- • Supports subtitles and multiple audio tracks
Weaknesses
- • Not ideal for professional editing
- • Less efficient than newer codecs
- • H.264 has licensing considerations
When to use MP4: Whenever you need maximum compatibility. Sharing videos, uploading to social media, playing on different devices. When in doubt, choose MP4.
MOV
Apple's format
Developed by Apple for QuickTime, MOV is the default format for iPhones, iPads, and Macs. It's technically similar to MP4—both derive from the MPEG-4 standard—but optimized for Apple's ecosystem.
Strengths
- • Excellent quality from Apple devices
- • Supports professional codecs like ProRes
- • Native editing support in Final Cut Pro
- • Can store higher-quality video than typical MP4
Weaknesses
- • Less compatible with Windows and Android
- • Often larger file sizes
- • May require specific codecs on non-Apple devices
When to use MOV: Within Apple's ecosystem or when preserving maximum quality for editing. Convert to MP4 when sharing with others.
WebM
The open web format
WebM is an open, royalty-free format developed by Google for web use. It uses VP8 or VP9 video codecs and Vorbis or Opus audio codecs.
Strengths
- • Completely royalty-free
- • Excellent compression with VP9
- • Native support in Chrome, Firefox, Edge
- • Optimized for web streaming
Weaknesses
- • Limited support on Apple devices
- • Not widely supported by media players
- • Less common than MP4
When to use WebM: Web development when you need a royalty-free format and can provide MP4 fallback. Popular for web animations and screen recordings.
MKV
The flexible container
MKV (Matroska) is an open-source container known for flexibility. It can hold virtually any video, audio, and subtitle format, making it popular for movie archiving.
Strengths
- • Unlimited audio and subtitle tracks
- • Supports almost any codec
- • Chapters and rich metadata
- • Open source and free
- • Excellent for movies with multiple languages
Weaknesses
- • Poor compatibility with mobile devices
- • Not supported by social media platforms
- • Requires specific software to play reliably
When to use MKV: Personal movie libraries where you want multiple audio tracks and subtitles. Convert to MP4 when sharing or playing on various devices.
AVI
Legacy format
AVI (Audio Video Interleave) was introduced by Microsoft in 1992. While largely obsolete, you may encounter AVI files from older cameras or archives.
Strengths
- • Wide Windows support
- • Simple structure
- • Compatible with older software
Weaknesses
- • Large file sizes
- • Limited codec support
- • No streaming support
- • Outdated technology
When to use AVI: Generally, don't create new AVI files. Convert existing AVI files to MP4 for better compatibility and smaller sizes.
Quick Comparison
| Format | Compatibility | File Size | Best For |
|---|---|---|---|
| MP4 | Excellent | Small–Medium | Everything |
| MOV | Good (Apple) | Medium–Large | Mac/iOS, Editing |
| WebM | Good (Web) | Small | Web embedding |
| MKV | Limited | Varies | Archives, Movies |
| AVI | Good (Windows) | Large | Legacy systems |
The Bottom Line
For most people, MP4 is the right choice. It offers the best balance of compatibility, quality, and file size. Use other formats when you have specific needs:
- MOV — Apple ecosystem and professional editing
- WebM — Royalty-free web video
- MKV — Movie archives with multiple tracks
- AVI — Only for legacy compatibility
Need to convert between formats? Convert Videos Free handles any video to MP4, directly in your browser.