Three steps: main video, optional second angle, then B-roll. Video 1 drives preview, audio, and export.
Works best with clips about 5 minutes and under 50 MB each; up to ~10 min / ~100 MB can work but export may be slow or fail on weaker devices. Auto-transcribe only hears the first ~30 seconds (server upload cap ~4 MB). Skip transcribe entirely — type your own B-roll search phrases (one per line) and click Re-fetch B-roll.
Set up your clips
1
Upload Video 1 — main clip + audio
Goes on the Video 1 lane. Shorter clips (under ~5 min, ~50 MB) are most reliable. Timeline appears in seconds; auto-transcribe runs in the background (optional).
No file yet → Video 1 lane + Audio lane
2
Upload Video 2 — second angle (optional)
Clap once on camera in both videos (before you speak), then use Sync on clap below — like Descript.
Upload Video 1 first
3
Auto-transcribe Video 1 → matching B-roll
After Video 1 uploads, we auto-transcribe the audio (Groq Whisper) and fetch matching free stock B-roll (Pexels) onto the B-roll lane.
Complete step 1 first
Timeline
Drag ⠿ from a library lane onto the Video 1 row. Trim with the green (start) and red (end) handles.
Video 1
Video 2 library
B-roll library
Audio
On a phone: drag across a clip’s filmstrip to highlight frames, or tap once on the filmstrip to select the whole clip. Then tap Place on Video 1 (or drag the yellow highlight onto the Video 1 row).
Selection:
B-roll library — preview & reorder
Drag clips to change playback order on the B-roll lane. Preview before dragging onto Video 1.
Main audio source: none yet.
Background music (optional)
Mixed under Video 1 narration at export. Built-in tunes are instrumental only.
Preview and export
Press Play to preview edits. After Export, review the finished MP4 below before downloading.
Six free articles (1,200+ words each) on YouTube editing, B-roll, two-camera sync, background music, and keyword stock. Start with how to edit YouTube videos for free.