MP4 vs WebM vs MOV: when to use each video format

People talk about video formats as if "MP4" and "MOV" are like JPG and PNG: two different ways to store the same kind of data. They are not quite. A video file is a container, and inside the container is at least one video stream and usually one or more audio streams. Each stream is encoded with a specific codec. So "MP4 with H.264 video and AAC audio" is a description of three things, not one.

That sounds tedious, but it is the reason a file can be "an MP4" and still not play. The container says MP4, but the codec inside is HEVC, and your player only supports H.264. Different problem, same symptom.

Containers vs codecs in one paragraph

The container is the wrapper. It says "this file contains video, audio, and subtitles, here is where each one starts." MP4, MOV, WebM, MKV, and AVI are containers.

The codec is the compression scheme used to turn raw pixels (or raw audio) into a manageable file. H.264, HEVC (H.265), AV1, VP9, and ProRes are video codecs. AAC, MP3, Opus, Vorbis, and PCM are audio codecs.

Most container/codec combinations are technically legal, but in practice a handful of combinations dominate.

MP4: the safe default

MP4 (technically ISO Base Media File Format) is the most compatible video container in the world. Just about every player on every device made in the last 15 years can play an MP4. The catch is that MP4 has been around long enough that the codec inside matters more than the container.

• MP4 with H.264 video and AAC audio: the universal default. Plays everywhere. Files are reasonably small. If you do not know what to pick, pick this.
• MP4 with HEVC (H.265) video: about 30 to 50% smaller than the same quality H.264, but playback support on older devices and many web browsers is incomplete. Default for iPhone recordings.
• MP4 with AV1 video: the newest, most efficient codec, but only recent hardware decodes it efficiently. Used on YouTube, Netflix, and Twitch's modern streams.

Use MP4 when: you are sharing a video with someone whose device you do not know, uploading to a wide range of platforms, or you want broad playback. Use H.264 inside if compatibility is the priority; HEVC if file size matters more.

MOV: Apple's house format

MOV is Apple's QuickTime container. Functionally it overlaps heavily with MP4 — they share most of the underlying structure — but MOV has additional features that matter for Apple's pro tools (Final Cut Pro, Motion, Logic).

Typical contents of a MOV file:

• H.264 or HEVC video (just like MP4) for general use.
• ProRes video, an Apple-developed editing codec. Very large files, very low compression artifacts, designed for color grading and timeline performance.
• Animation codec, an old Apple codec sometimes used for screen recordings.

Use MOV when: you are working inside Final Cut Pro or another Apple tool, exporting masters for editing, or you specifically need ProRes. For sharing? Almost never — convert to MP4.

If someone sends you a MOV and it will not play on Windows or Android, it is usually because the file uses ProRes or another Apple-specific codec. Converting the container to MP4 alone will not fix it; you need to re-encode the video stream to H.264.

WebM: the web's native format

WebM is the open container designed for the web, developed alongside HTML5 video. It is the format that <video> tags on websites prefer when both formats are available. WebM uses open codecs that do not have licensing fees — VP9 or AV1 for video, Vorbis or Opus for audio.

Strengths:

• Smaller files than the equivalent quality MP4 with H.264.
• Designed for browser playback, including features like Media Source Extensions used in modern streaming.
• Royalty-free, which matters for open-source projects and large platforms.

Weaknesses:

• Spotty support outside of browsers. Many video players, set-top boxes, and editing tools do not handle WebM well or at all.
• Sharing a WebM file with someone non-technical often ends with "I cannot open this."

Use WebM when: the destination is a website or a modern browser, and you want the smallest file size. Avoid WebM as a general-purpose share format.

MKV: the everything container

Although we did not name it in the title, MKV (Matroska) comes up often. MKV is the most flexible container of the bunch. It can hold almost any video codec, multiple audio tracks, multiple subtitle tracks, chapters, fonts for subtitles, and more. It is the default for ripping movies and TV shows, anime fansubs, and other places where multiple tracks matter.

The trade-off: Apple devices natively do not play MKV. Most Android devices do via VLC or MX Player. Smart TVs and set-top boxes vary widely.

Use MKV when: you are storing a video that has multiple audio tracks or subtitles you want to keep together. For sharing, convert to MP4.

M4V: the half-sibling of MP4

M4V is essentially MP4 with an Apple-specific extension. Files purchased from the iTunes Store usually have an M4V extension and may include FairPlay DRM. Renaming an .m4v file to .mp4 usually makes it play in non-Apple software, assuming the file is not DRM-protected.

A decision tree

When you have a video and you do not know what to export:

1. Is this for a website where you control the player? Export WebM (VP9 or AV1) and an MP4 (H.264) fallback.
2. Are you editing the video later? Export MOV with ProRes if you are on Apple, or MP4 with H.264 at a high bitrate otherwise.
3. Are you sharing with people on phones, laptops, or messaging apps? MP4 with H.264 video and AAC audio. Default for almost every situation.
4. Are you trying to fit a long video into a small file? MP4 with HEVC video, or WebM with AV1. Both halve the file size compared to H.264 if you have time for slower encoding.

Why your video file is huge

Video files are big because video data is enormous. A few quick numbers, all approximate:

• 10 minutes of 1080p H.264 video at standard bitrate: about 150 to 250 MB.
• 10 minutes of 4K H.264: about 600 MB to 1 GB.
• 10 minutes of 4K HEVC: about 300 to 500 MB.
• 10 minutes of 1080p ProRes: 5 to 8 GB. (ProRes is huge on purpose; it is an editing codec, not a sharing codec.)

If a video is unexpectedly large, the culprit is almost always one of: a high resolution (4K or above), a very high bitrate, an editing codec like ProRes, or a high frame rate (60 fps or above). Re-encoding to H.264 at 1080p 30 fps usually cuts the file size dramatically with a barely-visible quality change.