Datamoshing guide
What is datamoshing?
Datamoshing is a video glitch technique: you deliberately damage or remove parts of a compressed video’s data, so the codec gives up on drawing clean frames and smears motion from one shot straight into the next. That is where the melting, blooming, pixel-dragging look comes from, the one you have seen in music videos and glitch art for years. You can do it by hand in Avidemux or ffmpeg, in After Effects with a plugin, or with a purpose-built app like MOSH_UNIT that bends the compressed byte stream directly. No AI anywhere in it. Every pixel is still your own footage, just rearranged.
How does datamoshing work?
Here is the thing most people do not know about video files: they do not actually store every frame. A codec keeps a handful of complete pictures and fills the gaps in between with motion instructions instead, since that is way cheaper to store. Datamoshing just hijacks that shortcut. Pull out the complete pictures, or repeat the motion instructions past their point, and the decoder keeps applying old movement to footage it was never meant for. That is when the image tears, melts and blooms.
Three frame types make this possible. Once you know them, the whole trick clicks:
| Frame | What it stores | Role in datamoshing |
|---|---|---|
| I-frame (keyframe) | A full, standalone picture | Remove it and the decoder never refreshes, so motion from the previous shot bleeds in |
| P-frame | Only the change from the previous frame | Duplicate it and that slice of motion smears and blooms across the picture |
| B-frame | Change based on past and future frames | Less common in moshing, but the same idea |
What are the main datamoshing techniques?
- I-frame removal (the melt): strip the keyframes so a new scene gets painted with the motion of the old one. It is the classic transition where one shot dissolves straight into another, no cut in sight.
- P-frame duplication (the bloom): repeat frames that only hold motion data, so a single movement keeps pumping and blooming outward long after it should have stopped.
- AVI byte manipulation: edit the raw bytes of the compressed AVI file directly instead of cutting frames in an editor. Same result, different route in, and it is how MOSH_UNIT does it under the hood.
All three keep your original footage. Nothing gets generated: the glitch is still your own pixels, just moved to places the codec no longer knows how to draw them.
What does datamoshing look like?
- Bloom: motion piles up on itself and explodes outward into flowing, streaked trails. Repeat a P-frame enough times and one small gesture keeps blooming long after it should have stopped.
- Melt: one shot dissolves into the next with no hard cut and no crossfade. The old frame just keeps getting redrawn until the new picture finally takes over.
- Pixel drag: blocks of the image smear in whatever direction things were moving, like wet paint dragged across the frame. Panning shots drag the hardest.
- Freeze: a single frame locks in place while the rest of the clip keeps compressing around it, so the image looks stuck mid-motion.
What do you need to datamosh?
Two things: a clip with real motion in it, and a tool that can reach the compression data. Footage that moves, a pan, a person walking, a busy background, moshes far better than a static shot. A locked-off shot of a still object barely reacts, because there is no motion for the glitch to grab onto.
Source format barely matters. MP4, MOV, AVI and most common formats all work, because the tool re-encodes to a moshable form (long gaps between keyframes) before it touches anything. Length and resolution matter more: shorter clips are faster to experiment with, and you do not need 4K, since the glitch eats fine detail anyway.
Which tools can datamosh?
Most editors do not have a "datamosh" button, so people end up reaching for one of these instead:
- MOSH_UNITPurpose-built Windows app. Draw effects onto a clip, export MP4. $7.99, no After Effects.
- AvidemuxFree, cross-platform. Delete keyframes by hand. Technical but capable.
- ffmpegFree command-line tool. Total control if you are comfortable scripting.
- Adobe After EffectsPossible with a plugin or manual work, but a paid subscription.
Want a side-by-side on price and ease, or a full step-by-step walkthrough? Both are linked below. I built MOSH_UNIT because doing this byte editing by hand for every single clip got old fast, so if you would rather skip the hex editor, that is the shortcut.
Questions
- Is AVI byte manipulation real datamoshing?
- Yes, and this one comes up a lot. Classic datamoshing removes or duplicates frames so motion bleeds across cuts. Editing the AVI byte stream directly gets you to the exact same place: the compressed data gets altered so the decoder smears motion instead of drawing clean frames. It is a legitimate method, not a shortcut version, and it is how MOSH_UNIT works.
- Do I need After Effects to datamosh?
- No. After Effects is one route, but it needs a subscription plus usually a plugin or a lot of manual keyframe work. Avidemux and ffmpeg are free and get you there with no Adobe subscription at all, and a purpose-built app like MOSH_UNIT skips After Effects entirely.
- Does datamoshing use AI?
- No, and this trips people up because "glitch" and "AI" get lumped together a lot lately. Datamoshing is a compression trick, not a generative model. Every frame in the output comes from your own footage, just rearranged by the codec. MOSH_UNIT specifically has zero AI in it.
- Is datamoshing the same as glitch art?
- Not quite. Datamoshing is one branch of glitch art, specifically the video-and-compression branch. Glitch art is the bigger family, and it also covers things like image databending, pixel sorting and plain signal errors.