You paste a link, and the downloader answers with a list: MP4, WebM, M4A, sometimes the same size three times. Which one is right? The short answer is MP4. The longer answer helps you save space and avoid files that will not play.
Container and codec: two different things
The ending of a file, such as .mp4 or .webm, names the container: the box the video and the sound are packed in. What decides about quality and size is the codec inside: the method the picture was compressed with. The same picture can be packed in different boxes.
The containers
| Format | Good for | Plays on |
|---|---|---|
| MP4 | Everything. The safe choice. | Every phone, TV, computer and editing program |
| WebM | Small files for the web | Browsers, Android, VLC; not always on iPhone and TVs |
| MKV | Films with several sound tracks and subtitles | Computers and many TVs; rarely on phones without an app |
| M4A | Sound only (AAC) | Everywhere |
The codecs
- H.264 (AVC) is the oldest of the three and plays on anything made in the last fifteen years. Its files are the largest.
- VP9 needs about a third less space for the same picture. It is what YouTube uses for most HD and 4K videos.
- AV1 is the newest and the most economical. Recent phones and computers decode it; older ones stutter or show nothing.
AIOVideoDL writes the codec next to a size when it is VP9 or AV1. A size without a label is H.264.
Which file to choose
- For a TV, an old phone or for editing: MP4 without a codec label.
- To save space on a new device: the AV1 or VP9 version.
- For 4K and above: there is only VP9 or AV1. Use a current player such as VLC.
- For music and podcasts: M4A. See M4A, Opus or MP3.
Frequently asked questions
Is MP4 or WebM better quality?
Neither by itself. Quality depends on the codec and the bitrate inside. At the same size, a WebM with VP9 usually looks a little better than an MP4 with H.264.
Why does a video have no sound?
You picked a file from the list "video without sound". Those are for people who join the tracks themselves. Choose from the list with sound instead.
Can I turn a WebM into an MP4?
Yes, with free programs such as HandBrake or VLC. It is quicker to download the MP4 version in the first place.
