From the blog
MP4 vs WebM vs MKV: which format should you keep?
Formats are containers — boxes that hold video and audio streams. The box you choose decides where the file plays. Here is the practical comparison, without the codec lecture.
Published July 16, 2026 · All posts
In short
- MP4 holding H.264 video and AAC audio is the most compatible media file that exists — keep it unless you have a specific reason to want something else.
- WebM compresses better than H.264, but TVs, older devices, some phones and most editing software are far less reliable with it.
- MKV can hold multiple audio tracks, subtitle streams and chapters, which makes it ideal for archiving and a poor choice for sharing.
- Never “convert” upward: re-encoding a 480p WebM into a 1080p MP4 produces a bigger, blurrier file.
- If all you want is the soundtrack, a 192 kbps MP3 is smaller and plays everywhere.
MP4 — the default for a reason
MP4 holding H.264 video and AAC audio is the most compatible media file that exists: every phone, TV, browser, smart display and editing app made in the last decade plays it without plugins. File sizes are reasonable, hardware decoding means smooth playback on weak devices, and editors import it natively. Unless you have a specific reason to want something else, keep MP4 — which is why Simple Video Downloader remuxes downloads to MP4 by default.
WebM — the web-native one
WebM (usually VP9 or AV1 video) is what platforms like YouTube actually stream at higher resolutions, because it compresses better than H.264 — the same quality in a smaller file. The catch is compatibility: browsers love it, but TVs, older devices, some phones and most editing software are far less reliable. Keep WebM when the file will only ever live in a browser, or when storage genuinely matters more than compatibility.
MKV — the archivist’s container
Matroska (MKV) can hold nearly anything: multiple audio tracks, subtitle streams, chapters, any codec. That makes it ideal for archiving — and a poor choice for sharing, because plenty of stock players and editors refuse it. If you are building a personal library with subtitles and alternate audio, MKV is right; if you are sending a clip to a group chat, it is wrong.
The practical rules
Download at the best quality the source offers (Simple Video Downloader shows you what is available), and keep that file as your master copy. New to downloading? Our guide to downloading from any site covers the whole flow.
Audio-only is its own answer
If all you want is the soundtrack of content you have rights to, skip video containers entirely — a 192 kbps MP3 is smaller and plays everywhere. That is what the YouTube to MP3 converter produces.