Mainstream Video Formats Explained: MP4, WebM, MKV, FLV, AVI Feature Comparison

Video Container Format vs. Codec Format

Before introducing specific video formats, we first need to clarify two concepts: container format and codec format. Many people easily confuse the two.

Container format (such as MP4, MKV, AVI) is like a packaging box that can hold different things. It defines how video, audio, subtitles, and other data are organized and stored in the file.

Codec format (such as H.264, H.265, VP9) is the compression method for video and audio data, determining video quality and file size. The same container format can contain videos with different codecs.

Common Video Codec Formats

• H.264/AVC: The most mainstream video codec with the best compatibility
• H.265/HEVC: Higher compression rate, smaller files at the same quality
• VP9: Open-source codec by Google, commonly used in WebM
• AV1: Next-generation open-source codec with the highest compression rate
• MPEG-4: Older codec, gradually being replaced by H.264

Common Audio Codec Formats

• AAC: The most commonly used audio codec, standard for MP4
• MP3: Classic audio codec with good compatibility
• Opus: Open-source low-latency high-quality codec
• Vorbis: Open-source codec, commonly used in WebM
• AC3/DTS: Multi-channel audio, commonly used in movies

MP4 Format

MP4 (MPEG-4 Part 14) is currently the most mainstream video container format, supported by almost all devices and platforms. It evolved from the QuickTime format and was standardized by the MPEG organization.

MP4 Features

• Excellent Compatibility: Supported by almost all devices, browsers, and players
• High Compression Rate: With H.264/H.265 codecs, small files with good quality
• Streaming Support: Supports progressive download and streaming transmission
• Multi-Track Support: Can include multiple video, audio, and subtitle tracks
• Rich Metadata: Can embed title, description, cover art, and other info

Supported Codec Formats

• Video: H.264, H.265, MPEG-4, VP9 (partial support)
• Audio: AAC, MP3, AC3, Opus (partial support)

Use Cases

• Web video playback
• Mobile video
• Video sharing platforms
• General storage and exchange

WebM Format

WebM is an open-source, royalty-free video container format initiated by Google, designed specifically for web video. Its goal is to become the standard format for web video.

WebM Features

• Completely Open Source and Free: No patent fees required
• Small File Size: With VP9/AV1 codecs, high compression efficiency
• Web-Friendly: Native support in modern browsers like Chrome, Firefox, Edge
• Low Latency: Suitable for real-time communication and live streaming

Supported Codec Formats

• Video: VP8, VP9, AV1
• Audio: Vorbis, Opus

Use Cases

• Web video playback (especially Google products like YouTube)
• WebRTC real-time communication
• Projects sensitive to royalty fees
• Open-source projects and communities

MKV Format

MKV (Matroska) is an open-source, flexible video container format. Its biggest feature is supporting almost all codec formats and multiple tracks, earning it the reputation of a "universal container".

MKV Features

• Most Flexible Format: Supports almost all audio/video codecs
• Strong Multi-Track Support: Can include any number of video, audio, and subtitle tracks
• Feature-Rich: Supports chapters, menus, metadata, etc.
• Open Source and Free: Completely open standard
• Strong Fault Tolerance: Partially damaged files can still be played

Supported Codec Formats

Supports almost all audio and video codec formats, including:

• Video: H.264, H.265, VP9, AV1, MPEG-2, VC-1, etc.
• Audio: AAC, MP3, DTS, AC3, FLAC, Opus, etc.

Use Cases

• HD movie collection (Blu-ray, 4K resources commonly use MKV)
• Multi-language, multi-subtitle videos
• Video editing intermediate format
• Local video storage

FLV Format

FLV (Flash Video) is a video format developed by Macromedia (later acquired by Adobe). It was once the mainstream format for web video and live streaming. With the decline of Flash, FLV usage is decreasing, but it still has applications in the live streaming field.

FLV Features

• Small Size: Low encapsulation overhead, suitable for network transmission
• Fast Loading: Supports play while downloading, low startup latency
• Live-Friendly: Was the standard format for RTMP live streaming
• Simple and Lightweight: Simple format structure, easy to parse

Supported Codec Formats

• Video: H.264, VP6, Sorenson Spark
• Audio: AAC, MP3, Nellymoser

Use Cases

• HTTP-FLV live streams
• Some older video websites
• Low-latency live streaming scenarios
• Video surveillance (some devices still output FLV)

AVI Format

AVI (Audio Video Interleave) is a video format introduced by Microsoft in 1992, a classic format on the Windows platform. With the emergence of more advanced formats, AVI has gradually been phased out.

AVI Features

• Good Compatibility: Native support on Windows platform, good compatibility with older devices
• Simple Structure: Simple format, easy to handle
• Large File Size: Low compression rate, larger files at the same quality
• Limited Features: Doesn't support modern features like subtitles, chapters
• No Streaming Support: Must download the complete file to play

Supported Codec Formats

• Video: DivX, Xvid, MPEG-4, H.264 (non-standard)
• Audio: MP3, AC3, PCM, etc.

Use Cases

• Older devices and systems
• Output format of some surveillance devices
• Early video collections
• Scenarios that need to play on very old machines

Format Comparison Summary

Comparison Item	MP4	WebM	MKV	FLV	AVI
Browser Compatibility	★★★★★	★★★★	★☆☆☆☆	★★☆☆☆	★☆☆☆☆
File Size	Small	Smallest	Small	Small	Large
Multi-Track Support	★★★☆☆	★★☆☆☆	★★★★★	★★☆☆☆	★☆☆☆☆
Streaming Support	★★★★☆	★★★★☆	★★☆☆☆	★★★★★	☆☆☆☆☆
Open Source & Free	Partial	Yes	Yes	Partial	No
Recommendation Rating	★★★★★	★★★★	★★★★	★★★	★★

Browser Compatibility Details

For web video, browser compatibility is one of the most important considerations:

MP4 (H.264 + AAC)

• Chrome: Supported
• Firefox: Supported
• Safari: Supported
• Edge: Supported
• IE: Supported (IE9+)
• Mobile: Almost all supported

WebM (VP9 + Opus)

• Chrome: Supported
• Firefox: Supported
• Safari: Partial support (Safari 15+)
• Edge: Supported
• IE: Not supported
• Mobile: Android supported, iOS partial support

MKV

Major browsers don't natively support MKV format — JavaScript players (like the approach of flv.js, hls.js) are needed for web playback.

Format Conversion Recommendations

Web Publishing

Recommend using MP4 (H.264 + AAC) format for the best compatibility. If targeting only modern browsers, you can also provide a WebM version for smaller file sizes.

Local Collection

Recommend using MKV format — flexible codec selection, supports multiple audio tracks and subtitles, ideal for collecting HD movies.

Mobile

Recommend using MP4 format — good hardware decoding support, saves power and resources.

Live Streaming

Recommend using HTTP-FLV or HLS (TS segments) — low latency and good compatibility.

Format Conversion Tools

FFmpeg is the most powerful video format conversion tool, capable of converting between various formats. For example, converting MKV to MP4:

ffmpeg -i input.mkv -c copy output.mp4

If you don't want to use the command line, you can also use our online conversion tools:

• MKV to MP4 Online Tool
• WebM to MP4 Online Tool
• M3U8 to MP4 Online Tool

How to Choose a Video Format

When choosing a video format, consider the following factors:

1. Use Case

Is it web playback, local collection, mobile devices, or live streaming? Different scenarios suit different formats.

2. Target Audience

What devices and browsers do your users use? If you need to support older devices, MP4 is the safest choice.

3. File Size Limits

If there are strict requirements for file size, you can choose higher compression codecs (like H.265, AV1).

4. Feature Requirements

Do you need multiple audio tracks, multiple subtitles, chapter menus, etc.? MKV is the most powerful in this regard.

Summary

Each video format has its pros, cons, and use cases:

• MP4: The jack-of-all-trades choice with the best compatibility, suitable for most scenarios
• WebM: Open source and free, high compression rate, suitable for web and modern browsers
• MKV: Most feature-rich, suitable for HD collections and multi-track videos
• FLV: Still used in live streaming, suitable for low-latency scenarios
• AVI: An old format, recommended to gradually phase out

For most users, MP4 is the safest choice. If you have special needs, you can select the most suitable format based on the comparison above. When format conversion is needed, use our online video conversion tool — no software download needed for fast conversion.