Green screen file size limits — how big a file can you actually key?
Most online removers stop you at 100 MB, or 500 MB, or "up to three minutes". This one carries no number, because nothing is uploaded. Here is what that removes and what still stops you.
The short answer
This page imposes no file size limit and no length limit; drop in a multi-gigabyte clip and it starts. What limits you sits on your side: the memory available to the tab, the decoder in your browser, and two ceilings in the export path — a 1200-frame cap on the PNG sequence, real-time recording on the WebM.
An upload cap is a rule somebody wrote into a pricing page. These are properties of your machine, and you can work around most of them.
Why "no upload" removes the cap
An upload-based remover has to receive, store, render and return your file. Every step costs the operator money per gigabyte, so the free tier gets a ceiling and the paid tier a larger one. The cap is about their bill, not your clip.
Here the file never moves. The browser gets a local object URL, decodes frames with the Canvas API, keys each one and writes the result back out. No server in the loop means no cost to protect and nothing to meter. The no-upload page covers what that means for your footage; the privacy page says what is and is not collected.
The four limits that replace it
- Memory. A PNG sequence is assembled frame by frame in the tab's memory before the archive is written. Long clips at high resolution feel this first.
- The decoder. If your browser cannot decode the codec, the file is refused before keying starts, and the message names the readable formats.
- The 1200-frame ceiling. Only the sequence has it. It counts frames, not bytes: 1200 frames at any resolution.
- Real-time recording. Only the WebM has it. The export takes as long as the clip takes to play.
The frame ceiling, in seconds
The sequence caps at 1200 frames and you pick the rate, so the ceiling in seconds moves with the slider:
- 30 fps — 40 seconds
- 24 fps — 50 seconds
- 12 fps, the default — 100 seconds
- 1 fps — 1200 seconds
Go over and nothing is exported: the page refuses and names the rate that would fit. The projected frame count sits next to the slider before you start. Lower the rate, or trim.
The preview is capped. The export is not.
What you watch while dragging sliders is scaled down: the long edge of the preview is held at 1280 pixels whatever the source is. That is what keeps a slider responsive on a 4K clip. The export ignores it entirely — the transparent PNG and every frame of the sequence are written at the source's own pixel dimensions.
So a heavy file is not slower to tune than a light one; full resolution is paid for only at export. One consequence: the WebM rounds each dimension down to an even number, so an odd-sized source loses one row and one column there. The PNG exports do not.
What "no limit" actually costs you
Nothing here is free; the costs moved off a price list and onto your hardware:
- Full resolution, every frame. Nothing is downscaled on the way out; a long 4K sequence is a lot of pixels to key and a lot of PNGs to hold.
- The archive is stored, not compressed. The ZIP is stored, not deflated on top of the PNG encoding the frames already went through, so the download lands near the sum of the frames.
- The WebM is recorded, not rendered. It captures at up to 30 fps while the clip plays, at 8 Mbps. A ten-minute clip is a ten-minute wait, and a frame dropped mid-recording is gone.
- The whole job runs on your CPU. No render machine sits behind the page: a slow computer is a slow export.
Getting a long clip through
- Cut it first. Trim to the part that needs the key; that solves the frame ceiling and the memory pressure at once.
- Lower the sequence rate. 12 fps is the default and 8 or 6 is usually invisible in a matte that will be composited anyway. That buys minutes.
- Take the WebM for long clips. It has no frame cap. It costs real time and a lossy pass, but length is not the problem there.
- Downscale the source before it arrives. If the delivery is 1080p, keying a 4K original only makes every step heavier for pixels nobody will see.
- Close other tabs. The memory ceiling belongs to the tab, and a browser with forty tabs open has less to give.
Where the numbers on this site come from
Every keying measurement published here comes from a reference set of deterministic synthetic frames at 320×240 with hand-built masks, regenerated by a script so tables can be diffed when the algorithm changes. The CSVs live in the reference repository and the write-up is archived at doi.org/10.5281/zenodo.22916767.
Those fixtures measure whether a key separates subject from backdrop. They say nothing about size, throughput or codec quality, and they are far smaller than real footage — a 1080p frame is 2,073,600 pixels against 76,800, twenty-seven times as many. So this page quotes no megabytes per second: we have not measured it, and a guess dressed as a number is worse than no number. The benchmark page says what those tables do and do not cover.
When this does not work
- Your clip has no readable duration. A live or fragmented stream is refused before it starts. Re-encode it as MP4 or WebM first.
- The file has no video track. An audio-only file, or a container your browser decodes but finds no picture in, is rejected with that stated.
- Your browser cannot decode the codec. ProRes, HEVC in some browsers and odd camera formats will fail; there is no server-side fallback.
- You want the sequence and the clip is long. 1200 frames is fixed. Lower the rate or trim; the ceiling is not adjustable.
- You are short on memory. A long high-resolution sequence can exhaust the tab, and nothing here streams to disk.
- You need it faster than the clip plays. The WebM cannot be rushed, it records in real time. The sequence is not time-bound but is capped by frames.
- You expected the export to be downscaled. There is no output resolution picker: you get your source size and the file size that comes with it.
- You want a smaller file out than in. A stored-mode ZIP of full-resolution PNGs is the heavy path by design, the WebM is light and lossy, and there is no third option.
Try it on the file you actually have
Open the tool, drop the clip in and read the frame count next to the rate slider before you commit — it is the one number that decides whether the sequence runs. The PNG sequence vs WebM page covers which export to pick; the export settings page goes through what each keeps.