How to combine videos into one file

Check the order, choose a common frame and listen across every join. The filename extension tells only part of the story.

Choose a method that fits your clips

Use a sequence tool for a short set of clips, an editor for more layers, or stream copying for compatible recordings. Keep the original files until you have watched the whole result.

Join clips in your browser

Open the clips, confirm their order, then set the in and out points before exporting. File pickers can supply a different order from the one you expected.

1. Open at least two clips in the sequence studio. Read the numbered filmstrip.
2. Drag shots or use the earlier/later arrows. Select a shot to set Start and End.
3. Choose one output shape. Decide separately how each shot fits inside it.
4. Play through the sequence with sound. Check cuts before the first word and after the last word.
5. Save the result. Reopen it and check every join, including the last clip.

Floi makes a new 30 fps video and re-encodes its primary sound. It keeps files on your device and adds no watermark. The first release supports SDR clips, mono or stereo sound and a five-minute joined result.

Combine portrait and landscape clips without stretching them

Choose one output aspect ratio, then crop or pad each source. Stretching is a separate operation that changes the shape of faces and objects.

A 16:9 shot cropped to 9:16 at full height retains about 31.6% of its original picture area. That is a geometry calculation: (9 ÷ 16) ÷ (16 ÷ 9). Padding keeps all the picture. The aspect ratio guide explains these tradeoffs in more detail.

Keep sound with the shot it belongs to

A silent clip still occupies time on the joined soundtrack. The next clip’s sound must begin after that time, rather than immediately after the preceding sound ends.

• Keep the source picture and audio offsets together when trimming.
• Use silence for an intentionally silent shot. Do not remove its time from the audio sequence.
• Check a join that goes from sound to silence and another that returns to sound.
• Check the saved file too. Audio encoders can add priming or padding that a source preview does not reveal.

Floi builds its picture and audio on the same frame boundaries and corrects for the measured encoder delay. That does not repair sound already out of sync in a source. Add a new music bed afterwards with Add Audio to Video.

What we checked in the saved videos

On 1 November 2026, we joined original geometric practice clips in Chrome 156 on an Apple M1 Max with 32 GB memory. The sources were a three-second landscape clip with a 440 Hz tone, a two-second silent portrait clip at 24 fps, and a three-second square clip with an 880 Hz tone.

FFprobe counted the saved frames and track durations. FFmpeg decoded the audio. We measured tone frequencies inside each segment, away from codec boundaries. These short synthetic tests check timeline behaviour. They do not establish a browser memory maximum or prove support on Safari, Firefox or a physical phone.

Join without re-encoding when the streams match

FFmpeg can copy compatible encoded streams into one file. It avoids a fresh lossy encode, but matching .mp4 extensions alone are not enough.

The FFmpeg concat documentation requires matching streams, including codecs and time bases. Check dimensions, decoder configuration and audio layout as well. Mixed phone footage often needs a common encode.

Create a plain text file called clips.txt, listing local files in playback order:

file 'first.mp4'
file 'second.mp4'

Run this from the directory containing those files:

ffmpeg -f concat -safe 0 -i clips.txt -c copy joined.mp4

Only use a list you wrote and trust. Stream copying does not make mismatched streams compatible. If the output freezes, loses later sound or reports timestamp problems, use an editor to re-encode a consistent sequence.

Combine videos on an iPhone with iMovie

Start a Movie project in iMovie and select the clips you want to include. Arrange and trim them in the timeline, then export a new video. Apple’s combine videos instructions describe the current steps.

1. Create the Movie project and select your clips.
2. Check their order in the timeline. Adjust each clip’s edges to trim it.
3. Review the transition between each pair. Choose the transition you want, including a straight cut.
4. Watch the frame and sound, then save the finished video.

This is a useful option for phone footage, larger edits or clips a browser cannot decode. Desktop WebKit checks do not establish support on a physical iPhone. Keep a copy of your sources until the exported file has been reviewed.

What to check before sending the result

Watch a few seconds on both sides of each join. The total duration alone cannot tell you whether every segment survived.