Datamoshing guide
How to datamosh a video
Fastest way to datamosh: use a tool built for exactly this. Import a clip, draw where the glitch should hit, export an MP4, done. MOSH_UNIT does that on Windows for $7.99. If you would rather not spend anything, you can datamosh by hand in Avidemux or ffmpeg by removing keyframes yourself, or in After Effects with a plugin. Both routes are below, pick whichever fits your patience level.
The fast way: MOSH_UNIT (Windows)
MOSH_UNIT is a standalone app built only for this, nothing else it is trying to be. Runs on 64-bit Windows 10 and 11, works fully offline, and costs $7.99 as a one-time buy. These four steps are genuinely the entire workflow, there is no hidden step five.
Import your clip
Open MOSH_UNIT and drag a video onto the timeline. It reads MP4, MOV, AVI, MKV, WebM and more through the bundled FFmpeg, so there is nothing to convert first.
Draw the effect
Pick an effect (Bloom, Freeze, Reverse or Shuffle) and draw across the clip where it should hit. You paint the glitch on directly, no keyframes.
Stack and preview
Stack more effects onto the same zone and reorder them, then press preview to watch the glitch render. Reordering the stack changes the result.
Export an MP4
Export the result as an MP4 at highest quality. Your original audio is kept and stutters along with the effects, so picture and sound stay in sync.
The free way: Avidemux or ffmpeg
You can do this for free if you do not mind getting your hands into codecs a bit. The idea is always the same: encode to a format with sparse keyframes, then remove or repeat frames by hand.
- Re-encode your clip to an interframe codec (Xvid in an AVI works well) so it has long gaps between keyframes.
- In Avidemux, switch to copy mode and delete the I-frames (keyframes) where you want the melt to begin.
- Want a bloom instead? Duplicate P-frames so a single motion repeats and pumps outward.
- Save, then re-encode to MP4 for sharing. Expect trial and error here: some clips mosh beautifully, others barely react at all.
One thing trips people up: some codecs quietly re-encode the I-frame back in when you save, which undoes the whole effect. If your export looks clean where it should look broken, that is usually why. Stick to copy mode the whole way through.
ffmpeg can do all of this from the command line, and it is fully scriptable if you want to batch a whole folder of clips. Downside: zero visual feedback until you actually play the output back.
The After Effects way
After Effects can get you there too, with a paid plugin or a lot of manual frame work, but it needs an Adobe subscription and a genuine learning curve. If you already live in After Effects daily, sure, it is an option. If you just want the datamosh look and nothing else, it is the slow road.
Fast vs free, at a glance
| MOSH_UNIT (fast) | Manual (Avidemux / ffmpeg) | |
|---|---|---|
| Cost | $7.99, one-time | Free |
| Time to first mosh | Minutes | An hour or more of setup |
| Skill needed | None, you draw it on | Comfortable with codecs or the command line |
| Control | Named effects, stackable zones | Full, but entirely manual |
| Output | MP4 with audio, highest quality | Depends on your own export settings |