What is merging videos?

Merging videos, also called joining or combining them, puts several clips one after another in a single file. It turns the short clips a phone records into one video of a trip, joins the parts of a recording that was split, or adds an intro and an outro to a clip. Nothing is cut or rearranged inside the clips; they simply play back to back.

Tool description

This tool merges videos in your browser. Add two or more videos, drag them into the order you want, pick the size of the result, and save the merged video as an MP4. Each video is shown as a card with a thumbnail, its length, and its size, and you can preview any of them or the merged result in the player. Nothing is uploaded: the videos are processed on your device with FFmpeg compiled to WebAssembly.

Features

  • Merge any number of videos, including MP4, WebM, MOV, and other files your browser can play
  • Drag the cards to change the order, sort them by file name, or reverse them
  • Videos of different sizes and shapes are scaled to fit, with black bars instead of stretching
  • Choose the size of the result from the sizes of your videos, such as a landscape or a portrait one
  • Videos with different frame rates are brought to the same one, that of the smoothest video, up to 60 frames per second
  • Videos without sound get silence, so the sound of the others stays in sync
  • Preview each video, and the merged video once it's made
  • Saves as MP4 with H.264 video and AAC audio, which plays almost everywhere

How it works

The tool reads the length and size of each video in the browser. When you merge, FFmpeg first checks which videos have sound and what frame rate each one has. It then scales every video to fit the chosen size, pads it with black bars where the shape differs, converts it to the same frame rate, and joins the pictures and the sound with its concat filter. The joined video is encoded as H.264 with AAC sound.

Tips

  • Pick the size of your main clips. Making a small video larger won't add detail, and making a large one smaller keeps the file small.
  • To merge landscape and portrait clips without black bars, crop them to the same shape first.
  • All videos are re-encoded, so merging long or high-resolution videos in the browser can take several minutes and a lot of memory. Close other heavy tabs if it fails.
  • The first run downloads FFmpeg, about 30 MB. Later runs on the same page start right away.