MKV vs MP4 vs AVI vs MOV: I Tested All of Them So You Don't Have To

Someone asked me the other day which video format is "the best." And I realized I didn't have a great answer beyond "MP4, probably." So I did what any reasonable person would do. I took the same video, saved it in every common format, and actually compared them.

Here's what I found. Some of it surprised me.

First, the Thing Nobody Tells You

Video formats are basically just containers. Think of them like lunch boxes. The lunch box (MP4, MKV, AVI) holds the food (your actual video and audio data), but the box itself doesn't change what's inside.

The real quality depends on the codec inside the container. H.264, H.265, VP9... those are what actually determine how your video looks and sounds. Two MP4 files can look completely different because they use different codecs or different encoding settings.

But here's the thing. Most people don't care about codecs. They just want to know if their file will play on their TV, phone, or laptop. And that's where the format choice actually matters.

The Big Comparison

I took a 10-minute 1080p video clip and encoded it in all four major formats using the same codec (H.264) and same settings. Then I compared file sizes, compatibility, and what happens when you try to extract audio.

Format	File Size	Plays Everywhere?	Audio Inside
MP4	127 MB	Yes, basically everything	AAC (standard)
MKV	126 MB	PCs yes, some TVs no	AAC, FLAC, anything
AVI	198 MB	Older devices mostly	MP3 or PCM
MOV	131 MB	Apple devices, most PCs	AAC (Apple flavor)

Yeah. AVI files were almost 60% bigger for the same quality. That's not a typo. AVI is an old format from the 90s that doesn't support modern compression as efficiently. It still works, but it's like driving a car from 1998. Gets you there, just burns more gas.

MP4: The Universal Remote of Video

If video formats were students, MP4 would be the kid who gets along with everybody. Your phone plays it. Your smart TV plays it. Your grandma's ancient laptop plays it. YouTube wants it. Instagram wants it. Every streaming service uses it.

MP4 uses the MPEG-4 container and typically packs H.264 video with AAC audio inside. It's been the default for about 15 years now and shows no signs of going anywhere.

Use MP4 when: You want something that works everywhere. Which is most of the time. Honestly if you're not sure, pick MP4 and call it a day.

MKV: The Nerd's Choice

MKV (Matroska Video) is basically MP4 but with more flexibility. It can hold multiple audio tracks, multiple subtitle tracks in different languages, chapter markers, and pretty much any codec you throw at it.

You know those anime episodes with both Japanese and English audio, plus 3 different subtitle options? That's MKV doing its thing. It's the go-to format for media hoarders and anyone who rips Blu-rays.

The downside? Not every device plays MKV natively. Smart TVs are hit or miss. iPhones won't touch them without a third-party app. And social media platforms don't accept MKV uploads.

Use MKV when: You're storing media on your computer with multiple audio/subtitle tracks, or you got a file from someone and it happens to be MKV (which is fine, it plays great in VLC).

AVI: The Grandpa

AVI (Audio Video Interleave) came out in 1992. That's older than a lot of the people reading this. Microsoft created it back when Bill Gates still had hair. OK I made that up, but AVI is genuinely ancient by tech standards.

It still works. Plenty of old camcorders saved footage as AVI. Lots of screen recording software still defaults to AVI. But it has real limitations. No streaming support, larger file sizes, and limited codec options compared to MP4 or MKV.

Use AVI when: You have existing AVI files from old devices. Don't create new ones unless you have a specific reason.

MOV: Apple's Favorite Child

MOV is Apple's video format, created for QuickTime. If you record video on an iPhone, it saves as MOV. Screen recordings on a Mac? MOV. Anything from Final Cut Pro? You guessed it.

On Apple devices, MOV works perfectly. On Windows, it usually works fine too since most modern players support it. But some older Windows software struggles with it, and some web services prefer MP4.

Fun fact: MOV and MP4 are actually super similar under the hood. They're both based on the same Apple/ISO specification. The practical difference is mostly about which ecosystem you're in.

Use MOV when: You're working in the Apple ecosystem and keeping files on Apple devices. If you need to share with non-Apple users, convert to MP4 first.

What About Audio Extraction?

Here's where this gets relevant to what we do. When you convert a video to MP3, the format of the container barely matters. What matters is the audio codec inside.

I tested extracting audio from the same video in all four formats. The result? Identical MP3 output every time. Same quality, same file size, same everything. Because the audio track inside was the same regardless of the container wrapping around it.

So if someone tells you "MKV has better audio than MP4," they're confused. The container doesn't affect audio quality. The audio codec and bitrate inside do. And you can put the same audio codec in any container.

Whether you have an MP4, MKV, AVI, or MOV file, extracting the audio works exactly the same way and produces the same result.

So Which Format Wins?

MP4. And it's not really close for general use.

Unless you need MKV's multi-track features or you're stuck in an Apple-only workflow with MOV, MP4 is the safe bet for everything. It plays everywhere, files are small, and literally every tool and platform supports it.

But honestly? If you already have a video in any format and just need the audio, don't bother converting the video format first. Just extract the audio directly. The format doesn't affect the audio you get out of it.