Performance
Performance guidance for long videos and complex designs.
The video editor does all of its work in the user's browser, on the user's device. Preview and export speed therefore depend on that device, and on the length, the size, and the frame rate of the video.
Every export uses the same engine, which runs in the browser with the browser's own video and sound encoders. See Browser requirements.
Long videos
The export engine reads each source video in pieces, not as one whole file. A browser cannot read a file larger than about 2 GB in one piece, so this is what lets a source file of several gigabytes export. This is true for MP4, MOV, WebM, and MKV files.
The sound of a clip from such a file is read in pieces too, from the start of the file to the end of the clip. This works for Opus, AAC, FLAC, MP3, and PCM sound in MP4, MOV, WebM, and MKV files, and for Vorbis sound in WebM and MKV files. No browser can decode AC-3, E-AC-3, AC-4, DTS, TrueHD, MP2, or ALAC sound in pieces. A clip with such sound, from a file over about 2 GB, is exported without its sound, and the export list says so. It suggests a copy of the file whose sound is AAC or Opus.
A plain WAV or MP3 sound file over about 2 GB is not read in pieces. The export list says so, and suggests a copy under 2 GB.
The finished file is kept in memory while it is made, up to 512 MB. That is about 7.5 minutes of video at 9 Mbps. A larger file is written to the browser's private storage for your site instead, so memory does not run out.
A browser without that storage refuses such an export before it starts. The message gives the predicted size of the file, so the user can choose a lower bitrate or a shorter video.
Layer count
Each frame of the export draws only the items that are visible at that moment. An item that appears later in the video costs nothing on earlier frames.
Text and pictures are prepared once, before the first frame. A video clip must be decoded again for every frame it appears on. Several video clips visible at the same time are therefore the largest cost, and text, shapes, and pictures are small by comparison.
Export speed
The editor makes one export at a time, across every tab of your site in the same browser. Two exports at the same time would compete for the same hardware encoder and would each be slower, so a second export waits in the queue.
Thumbnails for onThumbnails are made after the video is finished and handed to onExport, so they never delay the video.
These Advanced settings in the Export panel change the speed:
| Setting | Effect on speed |
|---|---|
| Frame rate | Fewer frames per second means fewer frames to draw. Match source never makes more frames than the source has. |
| Sessions | Hardware and CPU together is faster than Hardware only. |
| Sizes | Each size is a separate video, made one after another. |
See Export for every option.