Which video format is better, MP4, WebM or MKV, is a question with no single answer, because people usually compare the wrong thing. The file extension tells you the container, while picture quality and compatibility depend on the codec inside it. The same MP4 can open everywhere or nowhere, depending on what is inside. Below we explain what a container and a codec are, how the three popular formats differ in practice, why Skachok always delivers MP4, and when a file can still refuse to open.
Container vs codec: what is the difference
A video file is built like a box with several tracks: video, one or more audio tracks, sometimes subtitles and chapters. The container is the box itself, the way the tracks are packed into one file and kept in sync. The .mp4, .webm and .mkv extensions describe exactly that container.
The codec is the compression method of a specific track. Video can be encoded in H.264, VP9, AV1 or HEVC; audio in AAC, Opus, MP3 or FLAC. The codec is what determines how large the file is, how good the picture looks at a given size, and whether your phone or TV can play it at all.
Containers differ in which codecs they can hold. That is where all the confusion comes from: "the MP4 won't open" almost always means "the player does not know the codec inside the MP4", not a problem with the format itself.
The three formats in practice
| Format | Typical codecs | Where it plays | Who uses it |
|---|---|---|---|
| MP4 | H.264 + AAC, less often VP9 / AV1 | almost everywhere | phones, cameras, social networks |
| WebM | VP8 / VP9 / AV1 + Opus | browsers, Android, PCs | YouTube, web players |
| MKV | anything | VLC, MPV, PCs, some TVs | archives, movie releases |
MP4 is the most widespread container. It is understood by iPhone, Android, Windows, macOS, TVs, game consoles and car head units. The standard pair inside, H.264 video and AAC audio, is decoded in hardware by almost every device released in the last ten years.
WebM was created by Google as an open format for the web. Inside you usually find VP9 or AV1 with Opus audio. It plays perfectly in Chrome, Firefox and on Android, but iPhones and many TVs ignore it, and Windows without extra codecs may play only the sound.
MKV (Matroska) is the most flexible container: it can hold any codec, several audio tracks, subtitles and chapters. That is why it is popular for archives and movies with multiple dubs. For the same reason it has the worst support in the built-in players of phones and TVs: there are too many possibilities for what might be inside.
What YouTube stores
YouTube encodes every video into several variants. Up to and including 720p there are "ready-made" MP4 files with H.264 and AAC. Above that there are only separate streams: video without sound and sound without video, the DASH technology. 1080p video streams exist in both H.264 and VP9; for 1440p and 4K often only VP9 or AV1 remains, because H.264 at that resolution is too heavy.
YouTube stores audio in two variants: AAC in an M4A container and Opus in a WebM container. That is where the M4A in Skachok's "Audio" block comes from: it is the original AAC track as is, with no re-encoding. The other audio options, MP3, OGG and FLAC, are built anew from the source track. More on how 1080p and above are assembled in the article on downloading in 1080p and 4K.
Why Skachok delivers MP4
We chose MP4 as our only video container for one reason: it opens on the largest number of devices without installing anything. Someone who has downloaded a video to a phone wants to open it in the gallery, not figure out why there is no sound.
Here is how it works:
- For 720p and below from YouTube and most platforms, we take the ready-made MP4 and serve it directly, without processing.
- For 1080p and above, the server downloads the video stream and the audio stream and then merges them into an MP4. There is no re-encoding: the tracks are simply repackaged, which is fast and lossless.
- If a platform serves video in another container, such as WebM or an HLS stream as Rutube (a Russian video hosting site) and Vimeo do, we also repackage it into MP4 without re-encoding.
- When choosing among streams of equal quality, we prefer H.264: such an MP4 is guaranteed to open anywhere.
The only case where the MP4 will contain something other than H.264 is high resolutions for which the platform simply has no H.264 variant. Then the MP4 will hold VP9 or AV1.
When an MP4 does not open
If a downloaded file will not play, the codec is almost certainly the culprit, not the container. The typical picture: a 4K YouTube video opens on a computer, but an older iPhone or the built-in Windows player shows a black screen.
What to do:
- Install VLC or MPV. Both are free, available on every system including iPhone and Android, and understand VP9, AV1 and any other codec.
- Download 1080p instead of 4K. At 1080p YouTube usually has an H.264 variant, and Skachok will pick it. On a phone or laptop screen the difference from 4K is invisible.
- Check the TV. Recent models with Android TV and webOS understand VP9; older ones do not. For an older TV, take 1080p.
You can transcode 4K from VP9 to H.264 in any video editor or converter, but it takes a long time and loses quality. It is simpler to pick the right resolution up front.
Which format to choose for different tasks
For watching on a phone or tablet: MP4 in 720p or 1080p. That is guaranteed H.264, minimal size and no playback problems.
For a TV: 1080p on any plan from Lite up, 4K on Max if the TV definitely supports VP9. On the YouTube page on Skachok all qualities are visible as soon as you paste the link.
For editing: the highest resolution available. Editing software handles VP9 and AV1 more slowly than H.264, but accepts them, and you will re-encode the material at render time anyway.
For audio alone: not a video format at all, but MP3 or M4A from the "Audio" block. Which one to take is covered in the article on downloading YouTube music to MP3. Quality terms for each plan are on the pricing page.
FAQ
Can I download video as WebM or MKV instead of MP4?
No, Skachok delivers video only as MP4, the most compatible container. You can repackage an MP4 into MKV or WebM locally without quality loss, for example with ffmpeg or any converter, in seconds.
Why won't an MP4 from YouTube open on my phone?
Most likely it contains VP9 or AV1, which is how YouTube stores 1440p and 4K. Install VLC or download the video in 1080p, where H.264 is usually available.
Is quality lost when repackaging into MP4?
No. Skachok does not re-encode video; it moves the tracks into another container as they are. Bitrate, resolution and codec stay the same as the source.
How does MP4 differ from M4A and OGG in the "Audio" block?
MP4 is video with sound. M4A is the same AAC audio track without video, delivered without re-encoding. OGG is the same track transcoded to Vorbis at around 192 kbps: handy for Telegram and Android, but it is a second round of compression.
Which format is best for a TV?
MP4 with H.264 in 1080p: it opens on any TV with a USB port. 4K in VP9 suits only recent models.