Remove a coloured background, with a preview that runs the export own arithmetic. Eyedropper colour picking, two named similarity measures, spill suppression, and a choice between a transparent MOV and a composite onto a new background.
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Record a screen, a window or a browser tab with system audio, your microphone, both or neither. The finished WebM carries its own length, so it seeks and scrubs where a plain browser recording reports no duration at all. Nothing is uploaded.
Cut a clip out of a video, choosing whether the cut lands on the exact frame (re-encodes to MP4) or leaves the streams untouched (instant and lossless, but only at a keyframe). The result says which ran and reads the real length back off the file.
Convert a video between MP4, WebM, OGG, MOV, AVI and MKV, each naming the codecs it really writes and each producing a file that actually plays. One quality dial normalised into four different encoder scales.
A talking-head clip shot on a green screen needs a new background for a web post.
Input
host.mp4 · key #00B140 · chroma, similarity 0.30, softness 0.10 · onto studio blue
Output
An ordinary H.264 MP4 that plays anywhere, subject on the new ground
Compositing is the default because transparency is expensive here and mostly unnecessary: the only format in this build that really carries an alpha channel is QuickTime RLE, which came out at 2.7 times the size of the source and which no browser will play. A WebM with VP8 accepts the request, writes a small file every browser plays, and silently discards the alpha, so it is not offered. The transparent MOV is there by name when the next step is an editor.
Remove a coloured background and either keep the transparency or composite the subject onto something else. The preview runs the export's own arithmetic rather than a lookalike, so what you see on the checkerboard is what ends up in the file.
Remove green screen backgrounds from talking-head videos and composite them onto custom scenes or branded backgrounds.
Film products against a green screen and composite them onto lifestyle backgrounds or clean white for e-commerce listings.
Export a WebM with real transparency and lay it over a page or another clip, which every current browser will play.
Export the lossless QuickTime file when the next step is a desktop editor and the file size does not matter.
Two things decide a chroma key and neither of them used to be named on this page. The first is what "similar" means. Measuring the distance in colour only, throwing the brightness away, keys a screen that is lit unevenly but painted one colour: a backdrop that is brighter at the top than the bottom is the same colour throughout, so it goes in one piece. Measuring the full RGB distance instead is exact on a flat generated background, such as a screen recording or an animation, and falls apart on filmed footage, because a shadow on the screen reads as a different colour and stays. Both are offered, both are named, and the page says which one is in force.
The preview used to disagree with the export, and not by a little. It measured a plain RGB distance against a threshold of the similarity times 2.55, which reads a percentage as a distance out of 255 on a scale that actually runs to 442; the export ran a filter that ignores brightness entirely and normalises by a different constant again. So 40 percent meant a radius of 102 on the canvas and 177 in the file. Both algorithms are now written out from the encoder's own source, so the preview is the export's arithmetic and the similarity is the number the encoder receives, on its own 0 to 1 scale rather than a percentage of something unstated.
The second decision is what can hold the result. Transparency needs a container that carries an alpha channel and a codec that encodes one. QuickTime RLE does, losslessly, and is enormous: measured here the picture alone came to 2.7 times the source and the whole file, with its uncompressed soundtrack, to 7.4 times, and no browser will play it. The obvious replacement does not work and does not say so: VP8 with an alpha-carrying pixel format in a WebM produced a 20,365 byte file that every browser plays and that carries no transparency whatsoever. Decoded back to raw pixels, 0 of its 307,200 were transparent and the background was still solid green, after a clean exit in about a second. So the transparent output is the QuickTime file, named with its cost, and compositing onto a colour or a picture of your choosing is the default for everything else. An MP4 cannot be transparent, and the page says so rather than producing one and hoping.
The edge is the third thing, and it is not optional. A hard threshold cannot key an antialiased or motion-blurred outline by construction: those pixels are genuinely part background, so a verdict of "keep" or "remove" is wrong either way and they need a partial alpha. The edge softness control sets the width of that ramp, the preview counts how many pixels ended up partly transparent, and the page warns when that count is zero, because a key with no soft pixels at all has cut the subject out with scissors. Spill suppression is a separate control for a separate job: it changes the pixels that STAY, pulling out the colour cast the screen throws onto the subject.
Raise the similarity, and watch the removed percentage under the preview rather than guessing. If the screen is lit unevenly, switch the measurement to colour only, which ignores brightness entirely; exact RGB keying is the one that struggles with a shadow on the backdrop.
Yes. Use the eyedropper to take any colour off the frame. Green and blue are standard because they are least likely to match skin tones, but any solid backdrop will do.
Raise the edge softness. At zero the key is a hard step, so a pixel is either kept whole or removed whole, and an antialiased or motion-blurred outline cannot come out clean because those pixels are part background by definition. The preview shows how many pixels ended up partly transparent, and warns when that is none.
A composite for anything going on a web page or into a post: it is an ordinary MP4 that plays everywhere. The QuickTime file when the next step is a desktop editor and the size does not matter, at 2.7 times the source for the picture and 7.4 times with its uncompressed soundtrack. There is no small transparent option here: the encoder that would have provided one accepts the request and silently drops the alpha.
Video is decoded and re-encoded on your own device. Large files never leave your machine.