Merge video files

Join two or more videos into one file in your browser. Matching clips are joined without re-encoding, so quality stays identical and it takes seconds.

Drop your files here

.mp4, .mov, .mkv, .webm, .avi · up to 300 MB

Choose files

How to Merge videos

1
Add two or more videos
MP4, MOV, MKV, WebM or AVI, up to 20 files. They merge in the order you add them.
2
Choose how the clips should join
Leave it on Auto and the tool copies streams when it can, or force fast copy or re-encode yourself.
3
Click Merge and download
One combined MP4 comes back, ready to save.

Fast copy versus re-encoding

When every clip shares the same codec, resolution, frame rate and audio format, the tool can copy the compressed streams straight into one file. No frame is decoded, so a pair of 50 MB clips joins in a few seconds regardless of length. The moment those parameters disagree, the picture has to be decoded and re-encoded to a single common format before it can share one timeline, which is roughly a hundred times slower. Auto mode checks compatibility for you and picks the faster path whenever it is available; forcing Copy on mismatched clips fails outright rather than silently degrading quality.

Different resolutions and missing audio

Re-encoding scales every clip to one shared frame size, the largest input by default or a resolution you pick, and letterboxes narrower footage with black bars instead of stretching it out of shape. If one of the clips has no soundtrack at all, that stretch of the merged file plays back as silence rather than jumping ahead, so the audio track never drifts out of sync with the picture.

Where re-encoding is worth it anyway

Normalize levels out loudness across clips recorded on different devices, which copy mode cannot touch since it never processes the audio stream. Combined with a shared resolution, it is the difference between a merged video that sounds and looks consistent and one that visibly changes character at every join.

Your videos never leave your browser

Both the fast-copy path and the re-encoding path run entirely on your device using WebAssembly and your browser's own video encoder. Nothing uploads to a server, there is no account and no queue, and closing the tab clears everything immediately.

Frequently asked questions

What is the difference between fast copy and re-encoding?

Fast copy moves the compressed video and audio streams into one file untouched, so it finishes in seconds with zero quality loss. Re-encoding decodes and recompresses every clip so they can share one format, which takes much longer but works even when the clips do not match.

Why is my merge being re-encoded instead of copied?

Copy only works when every clip has the same codec, resolution, frame rate and audio format. If any of those differ, the tool falls back to re-encoding automatically in Auto mode, or you can force either path yourself.

What happens if my videos have different resolutions?

Re-encoding scales everything to one shared size, by default the largest clip's resolution, and adds black bars to any narrower footage rather than stretching it out of shape.

What happens to the sound if one clip has no audio?

That portion of the merged file plays back as silence instead of skipping ahead, so picture and sound stay in sync across the whole result.

Why is the size limit different for fast copy and re-encoding?

Fast copy never decodes a frame, so the browser can handle much larger files quickly. Re-encoding holds decoded frames in memory, which is far more demanding and caps out sooner.