Remove a green screen and export video with a real alpha channel
Most online background removers hand you a video with a black or white backdrop baked in. Transparency Render keeps the transparency: it chroma keys your footage and encodes the result with a genuine alpha channel, so the clip drops straight onto any background in After Effects, Premiere, DaVinci Resolve, Final Cut, OBS or a web page. Drop in a file, pick the key colour, and export to WebM, MKV, ProRes 4444 or GIF.
It is free, needs no account, and nothing is installed. Your video is never uploaded — decoding, keying and encoding all happen on your own machine.
How it works
- Drop in a video. MP4, MOV, WebM, MKV, AVI and most other common containers are accepted.
- Pick the key colour. Use Pick color to sample the backdrop straight from the frame, or type a hex value. Green and blue screens both work, as does any other flat colour.
- Tune the key. Similarity sets how close a pixel must be to the key colour to be cut, Edge blend softens the boundary, and Despill removes the colour cast the screen throws onto your subject. The preview updates live on the GPU, and holding Original shows the untouched frame for comparison.
- Set in and out points, then export. Mark a section with I and O, loop it with L to check the key, then choose a format and press Export.
Output formats
| Format | Transparency | Best for |
|---|---|---|
| WebM · VP9 | Full 8-bit alpha | The best quality-to-size ratio, and the fastest export — it uses your browser's own hardware encoder. Needs WebCodecs (Chrome or Edge). |
| WebM · VP8 | Full 8-bit alpha | The widest compatibility, including older editors and browsers. Works everywhere, encodes more slowly. |
| MKV · VP8 | Full 8-bit alpha | The same video in a Matroska container, which some editors prefer. Can copy the original audio track untouched. |
| MOV · ProRes 4444 | Full alpha, 10-bit | Editing-grade masters for a professional NLE. Files are large — roughly 6 MB per second at 1080p — so keep clips to a minute or so. |
| GIF | 1-bit (on/off) | Stickers and quick loops. Edges are hard rather than soft and there is no audio. Length is limited by memory, not by a fixed cap — about 29 seconds at 720p and 15 fps, longer at a smaller size or frame rate. The panel tells you before you export. |
Your video never leaves your device
There is no server to upload to. The browser decodes your file, a WebGL2 shader does the keying and despill on your GPU, and the encoded result is written back to your downloads folder. Nothing is transmitted, stored or logged — which matters for client footage, unreleased material, and anything else you would rather not hand to a stranger's server. It also means there are no queues, no watermarks, and no file-size limit beyond what your own machine can hold.
Keyboard shortcuts
- Space play / pause
- A / D step back / forward one second (hold Shift for five)
- I / O set the in / out point
- L loop the selection
- S toggle chroma keying
Browser requirements
Chrome and Edge are the tested path and unlock every preset, including hardware-accelerated VP9 with alpha. Other modern browsers can still key and export through the built-in software encoder, but VP9 alpha is hidden where the browser cannot produce it. WebGL2 is required for the preview.
Questions
Is my video uploaded anywhere?
No. Every step runs locally in the browser tab. You can confirm it by loading the page, disconnecting from the network, and exporting anyway — it works offline.
Which format should I pick to keep transparency?
For the web, WebM with VP9 or VP8 — both carry a real alpha channel and play natively in browsers. For an editing timeline, MOV with ProRes 4444. Plain MP4 (H.264) cannot store transparency at all, which is why it is not offered here.
Why is my ProRes export so large, or refused outright?
ProRes 4444 has no rate control: file size follows resolution and duration rather than how compressible the picture is. Expect roughly 6 MB per second of 1080p footage, 3 MB at 720p, and about half again more than that from busy or grainy sources. Because the whole file has to fit in browser memory twice over to be assembled, ProRes is comfortable up to about a minute at 1080p, two minutes at 720p, or half a minute at 4K. An estimate is shown before you export, and an export that grows past what the browser can assemble is stopped early rather than failing an hour in. For anything longer, use WebM VP9.
Can I key a blue screen instead of green?
Yes. Any colour can be the key, and despill is applied automatically for green and blue backdrops. Flat, evenly lit backgrounds key best whatever the colour.
How large a file can I load?
Up to about 300 MB is comfortable. Larger files still load, but exports get slower and can run out of memory — trimming to the section you actually need is the reliable fix.
Does the preview match the exported file?
Closely, but not exactly. The preview reproduces the chroma key and despill maths; alpha blur is applied only at export, so soft edges come out slightly cleaner in the finished file than they look on screen.
Does it work on a phone?
It loads, but video encoding is heavy work and mobile browsers cap memory aggressively. A desktop browser is strongly recommended for anything longer than a few seconds.