Merge videos into one smooth MP4
You filmed a birthday in eight short clips, or recorded a course in three parts, and want one file to share. The clips have different sizes and orientations, so simple joining fails. Your todo.is agent matches them all to one format, joins them in your order, adds transitions or music if you want and returns a single video.
The prompt
- Merge the attached videos into one MP4: [ATTACH THE VIDEOS]. Order: [ORDER]. Make them all the same size: [OUTPUT FORMAT]. For clips with a different shape, [FIT OR FILL]. Between clips, use [TRANSITION]. Keep each clip's own sound at a similar volume, and [MUSIC]. Send me the final MP4 with its length, and a list of where each clip starts.
What to change
- [ATTACH THE VIDEOS]: Attach the clips (MP4, MOV, MKV, WebM; up to 50 MB each). Send them in several messages if needed.
- [ORDER]: E.g. "by the time they were filmed", "the order I sent them" or "intro.mp4, then part1, part2, outro.mp4".
- [OUTPUT FORMAT]: E.g. "1080p horizontal 16:9", "vertical 9:16 for phones" or "same as the first clip".
- [FIT OR FILL]: E.g. "blur the background to fill the space", "black bars" or "crop to fill".
- [TRANSITION]: E.g. "a half-second cross-fade", "a quick fade through black" or "straight cuts".
- [MUSIC]: E.g. "add the attached song quietly under the whole video", "no music" or "music only where clips are silent". Use music you have the rights to.
Example result
- Merge report: Mila's birthday
- 8 clips in · 1 MP4 out · 4:52 · 1080p horizontal · 30 fps · 168 MB
- Clip order (by filming time)
- • 0:00 · IMG_3301.MOV · arriving guests · 0:34
- • 0:34 · VID_2026_0912.mp4 · decorations · 0:21
- • 0:55 · IMG_3305.MOV · games in the garden · 1:12
- • 2:07 · IMG_3307.MOV · cake and candles · 0:48
- • 2:55 · VID_2026_0915.mp4 · singing · 0:39
- • ... 3 more, listed in Clip_list.txt
- Making clips match
- • Clips came from an iPhone (4K, 60 fps, HEVC) and an Android phone (1080p, 30 fps). All were converted to 1080p, 30 fps, H.264
- • 3 vertical clips: placed in the center with a blurred, enlarged copy of the same clip filling the sides, so there are no black bars
- • One clip was filmed upside down by mistake. Rotated
- Transitions and sound
- • Half-second cross-fade between clips
- • Each clip's own sound was leveled so the quiet garden clip and the loud singing clip feel similar
- • Your song plays at about 20% volume under everything, louder during the decorations clip where there was no talking, and fades out at the end
- Before you share
- • 168 MB is fine for Google Drive or a shared album. For WhatsApp, ask your agent for a compressed copy
- • Music: use songs you own or royalty-free tracks if you will post the video publicly
- Next ideas
- • "Add a title card: Mila turns 6"
- • "Make a 30-second vertical highlight version"
How to do it with todo.is
- Copy the prompt and set the order and the final shape.
- Attach all clips in todo.is on the Today screen, or send them to your agent on WhatsApp or Telegram as files.
- Your agent matches sizes and frame rates, joins the clips and balances the sound.
- Download the MP4, or reply "swap clips 3 and 4" or "no music" for a new version.
Tips for a better result
- Clips from different phones rarely match. Your agent converts all of them to one size and frame rate so the joins don't stutter.
- "By filming time" is the easiest order for events. Your agent reads the date and time stored in each file.
- Mixing vertical and horizontal clips? A blurred background fill looks much better than black bars.
- Name your intro and outro files clearly (intro.mp4, outro.mp4) so they always land in the right place.
merge videos: FAQ
- How do I merge videos with different sizes? Your agent scales every clip to one resolution and frame rate first, then fills or crops the clips that have a different shape.
- Can I add music when merging videos? Yes. Attach the music file and say how loud. Your agent mixes it under the clips' own sound and fades it out at the end.
- Does merging videos reduce quality? Clips are re-encoded to one format, at a high quality setting. You will not see a difference at normal viewing size.
- Can it merge vertical and horizontal videos? Yes. Pick a final shape, and your agent adds a blurred background or bars to the clips that don't match.
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