Question 1

Is it really not uploaded?

Accepted Answer

Yes. Loading, clipping, caption/BGM compositing and export are all processed only inside your browser (device). Your videos are never sent to an external server. An internet connection is only needed the first time you load this page.

Question 2

My exported video isn't MP4 / it's WebM.

Accepted Answer

The export format is limited to what your browser supports. Browsers that don't support MP4 recording produce WebM. The latest Chrome, Edge and Safari often let you choose MP4. To convert WebM to MP4, use a separate conversion tool.

Question 3

Export takes a very long time.

Accepted Answer

Because this tool records in real time at 1× speed, export takes roughly as long as the video's playback time (about 10 minutes for a 10-minute video). This is by design. Keep the tab open while exporting.

Question 4

Can I use 4K videos?

Accepted Answer

Yes, they load. However, editing and export are fixed at Full HD and sources are auto-scaled keeping their ratio. Handling many heavy 4K clips at once may stutter on some devices. If so, reduce the number of clips or use a more powerful device.

Question 5

My videos disappeared after reloading.

Accepted Answer

Your edits (clips, captions, BGM) are autosaved in the browser, but the actual video files cannot be saved (a browser limitation). Re-pick the same files via relink on the “Project” tab to keep editing as before. Saving JSON often is also recommended for important edits.

Question 6

Where are my edits saved, and when do they disappear?

Accepted Answer

They are autosaved in your browser's storage (LocalStorage) and remain after closing the tab. However, in secret/private mode they are lost when the tab closes. Always use normal mode, and save important projects to JSON.

Question 7

There's no sound / it's out of sync.

Accepted Answer

Press the play button via an on-screen action (a click). By browser rules, audio cannot play without a first user action. Also check each clip's volume and mute and the BGM volume. Export mixes audio while recording, so it is saved at nearly the same balance as during playback.

Question 8

How do I delete a clip or caption?

Accepted Answer

Hover over a block on the timeline and an × button appears at the top right. Press it to delete. Selected items can also be deleted with Delete/Backspace. If you make a mistake, undo with Ctrl+Z (⌘+Z on Mac).

Question 9

I made a mistake — can I undo?

Accepted Answer

Yes. Ctrl+Z (⌘+Z on Mac) undoes the last action. Redo is Ctrl+Shift+Z or Ctrl+Y. This covers adding/deleting/reordering clips and editing/moving captions and BGM (when the cursor is in a text field, that field's undo takes priority).

Question 10

I can't move a caption.

Accepted Answer

Drag the caption directly on the preview to move it anywhere. Where the cursor turns into a hand is where you can grab it. You can also place it quickly to one of top/middle/bottom × left/center/right from the 9-cell grid on the right “Captions” tab.

Question 11

How are caption and BGM times decided?

Accepted Answer

Press the “Now” button to set the start/end to the current playhead position. Line up the position first by playing or seeking, then set it, to match the exact scene you want.

Question 12

Are my videos or data sent anywhere?

Accepted Answer

No. From loading to export, everything is processed inside your browser, and your videos and input are never sent to any server.