Filewhisk

Merge videos into one

Drop two or more videos here

or click to choose — MP4, MOV, M4V, WebM, MKV. Drop more to add them to the end.

Drop in two or more videos, put them in order and download one file. When every clip has the same picture and sound settings (for example several clips from the same phone), they are joined without re-encoding: the frames are copied one after another, so it takes seconds and there is no quality loss. When they differ, the page says which clip and why, and re-encodes everything into one frame with black bars instead of stretching. Nothing is uploaded and there is no watermark.

How to merge videos

  1. Drop two or more MP4, MOV, M4V, WebM or MKV files into the box above. You can drop them all at once or one by one; each new file goes to the end of the list.
  2. Put them in order with the ↑ and ↓ buttons, and remove a clip with ×. Each line shows the clip’s length, picture size, frame rate and formats.
  3. Read the plan line. It says whether the clips can be joined without re-encoding, and if not, which clip differs and how.
  4. Press Merge videos, watch the result on the page, and download it.

When videos can be joined without re-encoding

Inside an MP4, the picture is a stream of compressed frames plus one small block of settings that the player needs to decode them: the codec, the picture size, and the encoder’s own parameters. If every clip carries exactly the same block, their frames can simply be placed one after another with shifted times, and a player cannot tell the result from a single recording. Nothing is decoded or encoded, so it takes seconds and the quality is exactly the original.

This page compares that block byte for byte, for both the picture and the sound, before it offers to copy. Clips filmed on the same phone in the same camera mode (same resolution, same frame rate, same HDR setting) normally match. A screenshot recording and a camera clip, a vertical and a horizontal clip, or a clip that has already been through an editor or a messaging app normally do not, and then the plan line names the first clip that differs from clip 1: a different picture size, orientation, codec, encoder settings or sound format.

When they cannot: one frame, no stretching

Clips that differ are re-encoded together. Every frame is drawn into one picture the size of clip 1 (so put the clip whose shape you want first), scaled to fit without stretching or cropping, with black bars where the shapes differ. The result is an H.264 video with AAC sound at roughly the bitrate of the original clips, which plays on every phone, computer and site. If some clips have sound and some do not, the silent ones get silence of their own length, so the sound of the later clips stays in sync with their picture.

What we measured

We ran each case through this page in Chrome and checked the merged file with a separate video library (PyAV). Our short test clips have their frame number drawn into every frame and a different tone in each clip, so the order of both picture and sound can be read back.

ClipsPathResultTime
Two 2 s clips, same settings, tones 440 and 660 Hzjoined without re-encodingall 120 compressed frames identical to the originals; clip 2 starts at 2.00 s; 440 Hz then 660 Hz0.03 s
Same two, order swapped with ↑joined without re-encoding660 Hz clip first–
320×240 clip with sound + 240×320 clip without sound, 25 fpsre-encoded320×240, 60 + 25 frames, 3.0 s; second clip with black side bars and silence0.85 s
The same 1080p phone video twice (2 × 12.16 MB)joined without re-encoding720 of 720 frames copied, 24.3 MB0.07 s
1080p landscape + 1080p portrait phone videore-encoded (“different orientation”)1920×1080, 720 frames, 24.3 MB, portrait clip with side bars12.1 s
Two Chrome screen recordings (WebM)joined without re-encodingstays WebM, 16 s–

Joining two matching 12-second 1080p clips took 0.07 seconds; re-encoding a landscape and a portrait clip of the same length took 12 seconds on the same laptop, about half real time. That is the whole difference between the two paths, and why the page tells you which one you are about to get.

Tips for a clean merge

  • Film in one mode. Same orientation, resolution and frame rate on every clip lets them join without re-encoding.
  • Cut first. Trim the start or end of a clip with Trim video before merging, and play the trimmed clip once to check where it starts.
  • Make shapes match. To avoid black bars, crop the odd clip to the same shape with Crop video, or turn a sideways one with Rotate video.
  • Too big to send? Shrink the merged file with Compress video.
  • Memory. The merged video is built in your browser’s memory. A few GB of clips is fine on a computer but may be too much for a phone.

Frequently asked questions

How do I merge videos into one?

Drop all the videos into the box (or drop them one at a time; each new one goes to the end). Use the arrows to put them in order, read the plan line, then press Merge videos. Play the result on the page and download it.

Does merging videos lower the quality?

Not when the clips match. If every clip has the same video format, picture size, encoder settings and sound format, the compressed frames are copied unchanged and only their times are shifted; the result card shows how many frames were copied. Clips from the same phone and camera mode usually match. If they do not, the page re-encodes them into one H.264 video at about the original bitrate, which costs a little quality, and tells you so before you start.

Why does the page say my clips cannot simply be joined?

A video file can only have one set of picture settings. A clip with a different size (a vertical and a horizontal video), a different codec (H.264 and HEVC), or even a different encoder setting cannot be glued onto another without re-encoding. The plan line names the first clip that differs from clip 1 and how. Recording all clips in the same camera mode avoids it.

What happens when the clips have different sizes?

The output takes the size of clip 1. Every other clip is fitted inside that frame without stretching or cropping, and the empty space is black. To make the result vertical, put a vertical clip first; to make it the same shape everywhere first, use Crop video on the odd one.

What if one clip has no sound?

When the clips are re-encoded, a clip without sound gets silence of the same length, so the sound of the following clips stays in sync with their picture.

Is there a watermark, a limit or an upload?

No watermark and no account. The videos are read and written by your browser on your own device, nothing is uploaded. The only limit is your device's memory: the merged file is built in memory, so several GB of video may be too much for a phone.

Which files work?

MP4, MOV, M4V, WebM and MKV that your browser can play. Matching MP4 or MOV clips come out as MP4, matching WebM clips as WebM; re-encoded results are always MP4 (H.264 and AAC), which plays everywhere.

Can I merge audio files too?

For MP3 files use Merge MP3. To cut a clip before merging, use Trim video.

Reverse Video Backwards or boomerang, every frame kept, no size limit. Change Video Speed The picture is copied, not re-encoded. Voices stay natural. MKV to MP4 Converter Same picture, new container. Subtitles and sound tracks are not lost on the way. Crop Video Drag a box, get exactly those pixels. Add Music to Video The picture is copied as it is. Only the sound is new. Compress MP3 Smaller MP3s, without making any file worse than it needs to be.