Turn an AI-generated clip into a transparent asset
Text-to-video models return a green or flat background because they cannot output alpha. Key it out here and get a transparent WebM, GIF, PNG sequence, or Lottie package, without uploading the clip.
Source: a green-screen keying sample
Synthetic sample · MP4 · 4 seconds · static subject
The sample keys its background and exports alpha WebM. On real generated footage, start from the AI-video preset and widen tolerance until the blocky edges clear.
Try this sampleThe problem
Video models do not produce an alpha channel. Ask any of the current text-to-video or image-to-video tools for a transparent subject and you get the next best thing they can encode: the subject on a green, blue, or flat neutral background, delivered as an ordinary MP4.
That footage keys differently from studio green screen. Generated backgrounds drift in shade across the frame, edges arrive already softened by the model, and heavy compression leaves blocky colour noise exactly where the matte has to be cut. A keyer tuned for a clean studio backdrop tends to leave speckle in the background or eat into the subject.
The usual fallback is a desktop editor, a round trip through After Effects or DaVinci for a four-second clip. That is a large amount of setup for an asset you may throw away after one look.
The browser workflow
EasyLottie ships an AI-video key preset with a wider tolerance and stronger despill than the studio-green preset, chosen for how generated footage actually degrades. It is a starting point, not a guarantee: the sliders stay available for tolerance, softness, despill, and choke.
Everything runs in the browser. The clip is decoded with WebCodecs and keyed on the GPU, so a short generated clip is a drag, a preset click, and an export, with no account and no upload.
Export as alpha WebM for the web, a PNG sequence when you want to composite in a real editor, transparent GIF for quick sharing, or a Lottie ZIP if your app already plays Lottie.
Complete the task
Generate with a plain background
When you prompt the model, ask for a solid green or a plain studio backdrop. An even, saturated background keys far better than a near-white one that blends into the subject.
Drop the MP4 in
Most generators export H.264 MP4, which decodes reliably in the browser. Trim to the seconds you actually want before keying.
Start from the AI-video preset
It opens with a wider tolerance and stronger despill than the studio-green preset. If the backdrop is not green, click the actual colour in the preview instead.
Clean up the compression noise
Raise tolerance until the blocky speckle around the subject disappears, then use choke to pull the edge back in and despill to remove colour that bled onto the subject.
Export and check on your background
Preview over the colour you will place it on before downloading. Generated footage often hides a faint halo that only shows against a dark background.
Common use cases
Hero and landing-page motion
Drop a generated character or object onto your own gradient instead of boxing it inside a rectangular video.
Overlays for edited video
Export PNG frames with alpha and composite the generated element over your real footage in any editor.
App and product animation
Package a short generated loop as a Lottie ZIP or alpha WebM for an onboarding screen or an empty state.
Frequently asked questions
Why can't AI video tools just export transparency?
The common delivery codecs they encode to do not carry an alpha channel, and the models are trained to produce complete frames. Returning the subject on a flat background is the practical workaround, which is why keying afterwards is a normal step rather than a failure.
Does this work on a generated clip with a real scene behind the subject?
No. This is colour keying: it removes one colour, not a subject. If the model put your subject in a room or a landscape, there is no single background colour to key and you need AI segmentation instead, which this tool does not do.
Which generators does this work with?
Any of them, because the input is just an MP4. What matters is the footage, not the tool that made it: an even, saturated backdrop keys well and a busy or near-white one does not.
The edges look chewed up. What should I change?
Lower tolerance first — an over-wide key eats the subject. Then raise despill to remove the colour cast on the rim, and add softness in small steps. Choke pulls the matte inward and is best used last and sparingly.
Is the clip uploaded to a server?
No. Decode, keying, preview, and export all run in your browser. Uploads happen only if you deliberately use cloud sync, a share link, or submit an error sample.
What if my generated clip is longer than the cap?
Output is limited to a 15-second selection and 450 frames, and MP4 or MOV sources longer than 30 seconds have to be trimmed outside the tool first. For a longer piece, key the section you actually need rather than the whole generation.