MOV vs MP4 comes down to where the video is going, not to picture quality. Use MP4 to share, upload or play a clip anywhere: almost every phone, TV, browser and upload form accepts it. Keep MOV, Apple's QuickTime format, for the originals from an iPhone and for editing in Apple apps. Both can hold exactly the same picture.
That last point needs a word of explanation. A video file is a box (a container) holding a picture track and a sound track, and the picture inside is squeezed by a codec, usually H.264 or HEVC. MOV and MP4 are two boxes that can carry the same codecs, so the same clip looks the same in either, and moving it from one to the other is often a quick copy rather than a fresh encode. MKV and WebM follow the same logic, each with a different strength.
The short answer: MP4 for sharing, MOV for Apple editing, MKV for archives, WebM for the web
When in doubt, use MP4. Mozilla's reference for web developers calls it the industry standard for video content, widely supported across devices and browsers, and notes that QuickTime support is mainly found on Apple devices. Each of the other formats wins in one place:
- MP4 when the clip leaves your device: email, chat, a website upload, a TV, a Windows PC or an Android phone.
- MOV when the clip stays with Apple: the original from your iPhone, or a project in an Apple editing app.
- MKV when one file must hold everything: several sound languages, subtitles you can switch on and off, chapters.
- WebM when the video plays on your own web pages and you want open, royalty-free formats.
| MP4 | MOV | MKV | WebM | |
|---|---|---|---|---|
| Defined by | ISO (MPEG) | Apple | The IETF, as RFC 9559 | The WebM Project |
| Picture usually inside | H.264 | H.264 or HEVC; ProRes for editing | Almost any: H.264, HEVC, VP9, AV1 | VP8 or VP9 |
| Sound usually inside | AAC | AAC | Almost any | Opus or Vorbis |
| Best for | Sharing and uploading | iPhone originals and Apple editing | Archives with many tracks | Video on web pages |
| Where it struggles | Rarely | Outside Apple devices | Players that do not read Matroska | Some apps outside the browser |
MOV vs MP4
What is a MOV file?
A MOV file is a QuickTime movie. The Library of Congress describes the QuickTime file format as a format developed by Apple that wraps video, audio and other streams, with the .mov ending for movie files. Apple still builds on it: its recording toolkit for iPhone and Mac apps records video and audio to a QuickTime movie file, and clips from an iPhone camera arrive as .mov files.
Quality and file size
Neither format is sharper in itself. Quality comes from the codec and from how much data per second it is given, not from the box. The two boxes are also close relatives: MP4 is built on the ISO base media file format, which the Library of Congress notes is directly based on Apple's QuickTime container format. So the same H.264 picture can move from a MOV into an MP4 untouched, and the file size barely changes.
One case favours MOV: editing. Apple's ProRes codecs are made for editing rather than sharing, and the Library of Congress notes that QuickTime is a common wrapper for ProRes. If a camera or an editor hands you a ProRes MOV, keep it as your master copy and share an MP4 made from it.
When to convert MOV to MP4
Convert when the clip has to leave Apple's world: a Windows PC, an Android phone, an upload form that lists MP4, a TV playing from a USB stick. Our convert MOV to MP4 page looks at what is inside first. A MOV holding H.264 is repackaged, so nothing is lost and it is quick. A MOV holding HEVC, which iPhones record under the High Efficiency camera setting, is re-encoded once to H.264 so the MP4 plays as widely as possible.
MKV vs MP4
What is an MKV file?
An MKV file uses Matroska, an open container format. In October 2024 the IETF published its specification as RFC 9559, which calls Matroska an envelope that can hold many audio, video and subtitle streams, with chapter entries too. So one MKV can carry a film with several sound languages, a commentary track and subtitles you switch on and off.
That flexibility is why people archive in MKV, and it is also the weak spot. Support for Matroska is up to each player, TV and app, so before you send an MKV, check that the place it is going lists MKV or Matroska among its formats. If it does not, send an MP4.
When to convert MKV to MP4
Convert when a device or a website will not take the MKV. Our convert MKV to MP4 page copies an H.264 picture straight across with no loss and re-encodes anything else, such as HEVC, VP9 or AV1, to H.264. The MP4 keeps one picture track and one sound track; extra languages and subtitle tracks are left out. Keep the MKV as your archive copy and share the MP4.
WebM vs MP4
What is WebM?
WebM is an open media format designed for the web. The WebM Project describes WebM files as VP8 or VP9 video with Vorbis or Opus sound, in a file structure based on Matroska, and says Google does not demand royalties for those codecs. Think of WebM as a slimmed-down MKV with a fixed set of free codecs.
So which should you use? In a web browser, both play. Mozilla's guide to web video codecs calls MP4 with H.264 video and AAC sound a broadly supported combination, supported by every major browser, and that same pair is what most phones, TVs and editing apps expect. Use WebM for video on your own web pages when open formats matter to you; use MP4 for everything else.
When to convert WebM to MP4
WebM often comes from screen recorders that run in a browser, and an editor or a phone may not open it. Our convert WebM to MP4 page always re-encodes the picture to H.264, so the Quality setting matters: Balanced for sharing, Best if you will edit the result. Going the other way, MP4 to WebM is always re-encoded too.
How to convert between them
Our video converter turns any of these into MP4, WebM, MOV or MKV inside your browser, so the video is never uploaded. Drop the file in, choose the format under Convert to, pick a Quality (Smaller, Balanced or Best, each with an estimated size) and press Convert. It works in current Chrome, Edge and Firefox, and adds no watermark.
Whether you lose anything depends on what is inside the file, not on its ending. This is what our converter does to the picture:
| From | To | The picture |
|---|---|---|
| MOV with H.264 | MP4 or MKV | Copied as it is: no loss, and quick |
| MOV with HEVC (High Efficiency) | MP4 or MKV | Re-encoded once to H.264 |
| MKV with H.264 | MP4 or MOV | Copied; extra sound and subtitle tracks are left out |
| MP4 with H.264 | MOV or MKV | Copied as it is |
| WebM (VP8 or VP9) | MP4, MOV or MKV | Re-encoded to H.264 |
| MP4, MOV or MKV | WebM | Re-encoded to VP9 (VP8 for files that take longer) |
The sound follows the same rule. AAC sound is copied into an MP4, MOV or MKV, and other sound is re-encoded to AAC; a WebM always gets Opus sound. If the result is still too large to send, compress the video afterwards. For a clip going to TikTok, Instagram, YouTube or LinkedIn, the shape and length matter as much as the format: see our guide to social media video sizes.
Worth knowing
Recording on an iPhone? Apple's guide to HEIF and HEVC media shows the switch: Settings, Camera, Formats, then Most Compatible makes new videos H.264 instead of HEVC. Those MOVs then become MP4s by a quick copy, at the cost of bigger files on the phone, because Apple says HEVC uses less storage for the same visual quality. Apple also notes that video may be turned into H.264 automatically when you share it or import it over USB.
Every conversion writes a new file and leaves the original as it was. Keep the original when you can: each re-encode compresses the picture again, so converting a clip back and forth costs a little detail every time. We read every outside source linked in this guide on 22 October 2026.
MOV, MP4, MKV and WebM questions
Is MOV better quality than MP4?
No. Both are containers, and the picture quality comes from the codec inside and how much data it is given. A MOV and an MP4 holding the same H.264 picture look identical. MOV only pulls ahead when it carries an editing codec such as Apple ProRes, which is made for editing rather than for sharing.
Why are iPhone videos MOV?
Because the iPhone saves video as a QuickTime movie, Apple's own format, which ends in .mov. Inside is HEVC under the High Efficiency camera setting, which Apple recommends because it uses less storage for the same visual quality, or H.264 under Most Compatible. The ending stays .mov either way.
Can every device play MKV?
No. Matroska is an open standard, but each phone, TV, console and app decides for itself whether to read it. Look for MKV or Matroska in the device's list of supported formats. If it is not there, convert the file to MP4, which plays almost everywhere.
Is WebM the same as MP4?
No. WebM is based on Matroska and holds the open VP8 or VP9 video codecs with Vorbis or Opus sound. MP4 is an ISO standard that usually holds H.264 video and AAC sound. Both play in current browsers, but outside the browser MP4 is the safer choice.
What is the best video format?
For most people, MP4 with H.264 video and AAC sound. Every major browser supports it and almost every device plays it, so it is the safe choice whenever you do not know where a file will be opened. Use MOV for Apple editing, MKV for archives with many tracks and WebM for video on your own web pages.