How this tool works
Add the clips, put them in the order you want, and they are written into one file. Anything your browser can open is accepted — clips of different sizes, shapes and frame rates can be joined without preparing them first, because they are made to match rather than being refused. Nothing is uploaded; the work happens on your own device.
Joining is not the same as sticking two files together. Videos can only share a container if they share a resolution, a frame rate and a codec, and clips from different sources almost never do. So every clip is re-encoded into one common target. The list says what will happen to each one — scaled, reshaped, or given silence where it has no sound — before anything is encoded, so there are no surprises after the wait.
How mismatched clips are handled
- The output shape follows the first clip by default: that is usually the main video, and an intro or an outro should adapt to it rather than the other way round. You can choose a fixed shape instead when the result is going somewhere specific.
- A clip of a different shape is filled, not stretched: blurred fill scales it to fit and puts a blurred copy of it behind, so nothing is cropped and nothing is black. Stretching a clip to force it into the wrong shape looks wrong to everybody, so it is not offered.
- Silence is written for clips that have none: if one clip in the middle has no audio and nothing were written for it, the sound and the picture would drift apart for everything after it. Silence of exactly the right length keeps them together.
- Order is set here, not by file name: clips join in the order shown and can be moved up or down. Selecting several files at once adds them in whatever order the browser hands them over, which is worth checking before starting.