MP4, MOV, MKV, or WEBM: Video Format Differences

The format is the container; the codec is what's inside

To understand why a video plays in one place but not another, it helps to separate two concepts:

• Format (or container): This is the "container" indicated by the file extension: .mp4, .mov, .mkv, .webm. It holds the video and audio tracks, subtitles, and details such as the duration.
• Codec: This is how the picture and sound are compressed inside the container. Common video codecs include H.264, HEVC (H.265), VP9, and AV1; common audio codecs include AAC, MP3, and Opus.

A device needs to support both the container and the codec. Many "unsupported format" issues are actually caused by an unsupported codec.

MP4: the universal standard

MP4 is one of the most widely compatible formats: phones, computers, TVs, social media platforms, messaging apps, and video editors can all open it. Pair it with the H.264 codec and AAC audio, and it works almost everywhere. It's the right choice when you don't know where the video will be played.

Keep in mind: an MP4 with HEVC inside is less compatible than an MP4 with H.264.

MOV: Apple's format

MOV was created by Apple and is the standard format for iPhone videos and many Mac apps. Technically, it's very similar to MP4. It works well on Apple devices; on Windows PCs and TVs, the problem is often the HEVC codec used by default on iPhones, not the container. In these cases, changing the file extension isn't enough: you need to re-encode the video. Compress video does this when it creates a new MP4.

MKV: flexible, but not widely supported

MKV (Matroska) is an open, highly flexible format. It can hold multiple audio tracks (for example, dubbed and original audio), multiple subtitle tracks, and chapters in a single file. That's why it's common for downloaded videos and game recordings.

The downside is compatibility: phones, messaging apps, social media platforms, and many TVs don't support MKV. To use your video in these places, convert it with MKV to MP4. If the video already uses a compatible codec, the conversion just changes the container, with no quality loss, in seconds.

WEBM: the web format

WEBM was created for online video and uses open codecs (VP8, VP9, AV1). It's the format browsers often create when recording your screen or camera. It works in browsers, VLC, and many video editors, but has limited support on older iPhones, in messaging apps, and in some software. To share it, convert it with WEBM to MP4.

Which option to choose for each situation

• Send to someone, post online, or play on a TV: MP4 with H.264.
• Keep the highest quality without needing to share right away: the camera's original format.
• Archive a movie with multiple audio tracks and subtitles: MKV.
• Publish on your own website: MP4, with WEBM as an optional, smaller alternative.

To convert between these formats in either direction, use Convert video, which supports MP4, WEBM, MOV, and MKV.

What about AVI, WMV, and 3GP?

These are older formats. AVI and WMV show up in videos from older cameras and computers, while 3GP was used on older phones. They still open in programs like VLC, but MP4 is a better choice for sharing today.

How to find a video's format and codec

The file extension tells you the format, but not the codec. To see what’s inside:

• VLC (desktop): open the video and go to Tools › Media Information › Codec tab. You’ll see the video and audio codecs, resolution, and frame rate.
• Windows: right-click the file › Properties › Details to see the resolution and bit rate; the codec may not appear.
• Mac: in Finder, select the file and choose Get Info; the More Info section shows the codecs.

Knowing the codec can help you avoid unnecessary conversions: an MKV containing H.264 only needs to be repackaged, while an MP4 with HEVC needs to be re-encoded to play on older devices.

Frequently asked questions