Export settings

Export has three visible choices — resolution, frame rate, length — and one invisible one, the bitrate, which is derived from the other two. Here is what each does to the file that lands in your downloads folder.

Resolution and frame rate

Export at 1080p unless you have a reason not to. It is the shape everything downstream is built for, it plays everywhere, and past it you are mostly making a bigger file of the same screen recording. 720p is worth choosing when the file has to be small — an email attachment, a slow connection — and 1440p or 2160p when the demo will be shown on a large display or you want headroom for someone else to crop into it. There is no point exporting above your source: enlarging a 1080p recording to 2160p adds file size and no detail. The default is set to the largest standard height your source can actually fill.

How the bitrate is chosen

You do not set it, because the useful number depends on frame size and frame rate together and picking it by hand is how people end up with a blocky 4K file. It is computed at roughly **6.2 Mbps per megapixel**, multiplied by 1.5 above 30 fps, and clamped between 4 and 48 Mbps. For 1080p at 30 fps that lands around 13 Mbps, which is generous for screen content — flat interface backgrounds compress extremely well, and the extra headroom is what stops gradients from banding. Screen recordings are unusual that way: they need less bitrate than camera footage for detail, and more of it than you would expect for smooth flat areas.

MP4, H.264, and keyframes

The output is an MP4 with H.264 video and, if present, AAC audio at 128 kbps — the combination that plays everywhere without a conversation. The encoder prefers the High profile, falls back to Main, then Baseline, because Baseline lacks the tools that keep flat backgrounds from banding and this app puts your recording on exactly those flat backgrounds. Frame dimensions are forced to even numbers, because H.264's colour subsampling does not accept odd ones. A keyframe is written every two seconds, which is what makes the file seek smoothly when someone drags the scrubber.

When export is not available

Encoding uses WebCodecs, which in practice means Chrome or Edge on a desktop. There is no fallback path — no WebM, no GIF, no server-side encode — and rather than half-working, the app tells you before you press export. Recording and editing still work in browsers that cannot encode, so you can prepare there and export elsewhere. The export itself is not a real-time capture: every frame is seeked, drawn and encoded individually, so a 30-second demo takes a while and the result is frame-exact rather than dependent on how fast your machine was during playback.