Exporting to mp4

The timeline is a recipe: instructions about which clip appears when and with what effects. Your browser re-cooks it every time you press play. But you can't upload a recipe to YouTube or send it to a friend — for that you need one finished file. Export is what makes it: it turns the whole recipe into a single mp4.

The important part: all of this happens on your own machine. Your video is never uploaded, never sent to any server — the browser draws the frames, assembles the mp4 and saves the finished file straight to your disk.

The export settings

Press “Export” at the top and a small dialog opens. There are three settings, and most of the time you don't need to touch any of them: the defaults are already right.

Exporting just a slice

Want a single scene rather than the whole project — a short clip pulled out of a long video, say? Mark a play range.

Set the start of the range at the playhead

I

Set the end of the range at the playhead

O

Play back just that range to check it

Space

Once a range is set, a “Selected range only” option appears in the export dialog. Turn it on and only that slice is rendered — and the resulting file still starts at zero seconds, with no empty run-up at the front. You can also drag the range handles along the top of the timeline.

Audio: everything is mixed into one

During export all of your audio tracks — the voice, the music, the sound that came with the videos — are summed into a single soundtrack. This is called a mixdown: dozens of separate sources become one final audio stream.

Every choice you made goes into that mix: track and clip levels, fades, audio effects, mute and solo. In other words, what you hear in the preview is what lands in the file. Give the sound one full listen before you export.

The wait: how long, and why

Export isn't an upload — it's computation. The browser redraws every single frame: decode the video frame, apply the effects, lay the text on top, then compress it and append it to the mp4. One minute at 30 fps means doing that 1800 times.

• What makes it slower: a big height (4K), a high frame rate, many layers, effects, transitions and — of course — the length of the video.
• What makes it faster: a stronger machine and a smaller height. For a test run export at 720p, and once everything checks out, re-export at 1080p.

Browsers: what works and what doesn't

Export leans on a browser feature called WebCodecs — a fairly new technology that lets code compress video directly. Support for it is not the same everywhere.

Common questions