Merge Videos (Video Joiner)
Put several clips together into one video — losslessly when they match.
Clips
Drag a clip by its handle to change the order, or use the arrow buttons. With the handle focused, ↑ and ↓ move the clip.
How to join
These clips cannot be joined without re-encoding:
What will happen
About the Merge Videos (Video Joiner)
Join two or more video clips into one file, in the order you choose: drag clips by their handle (or use the arrow buttons) to arrange them, then merge.
When all clips come from the same phone, camera or app with the same settings, they are joined without re-encoding: the original video and audio data are copied one after another, so it takes seconds and the quality is untouched. When the clips differ — another resolution, frame rate or codec — the page says exactly why and re-encodes them to one format: you choose the output size, how clips of a different shape fit (black bars or crop to fill), the frame rate, and optional crossfades or black gaps between clips. Even out the volume measures each clip’s loudness (ITU-R BS.1770) and adjusts quiet and loud clips to match. Everything runs in your browser; nothing is uploaded.
How to use it
- Drop your videos on the box or click Choose videos (you can add more later with Add videos).
- Arrange the clips: drag a clip by its handle, or use the ↑ ↓ buttons. Remove clips with ✕.
- Keep Join without re-encoding when it is available, or choose Re-encode to one format and pick the size, fit, frame rate, format and transition.
- Optionally tick Even out the volume, check What will happen, and press the join button. Watch the result and Download it.
Examples
3 iPhone videos · 1920×1080 · 30 fps · HEVC + AAC
One MOV with all three in a row, joined in seconds without re-encoding
A 1920×1080 phone clip, a 1280×720 screen recording and a vertical 1080×1920 clip · Same as clip 1 · Fit (black bars) · Crossfade 1 s
A 1920×1080 H.264 MP4 at clip 1’s frame rate; the vertical clip appears in the middle with black bars at the sides, and each clip fades into the next
4 clips, one recorded much further from the microphone · Even out the volume
Each clip measured in LUFS and turned up or down towards the clips’ median loudness; no clip is turned up past a sample peak of about −0.2 dBFS
When can clips be joined without re-encoding?
A video file has one setup for each track: codec, profile and level, the encoder’s parameter sets, the frame size and rotation, and for the sound the codec, sample rate and channels. Clips with exactly the same setup — typically recorded on the same device with the same settings — can be copied one after another into one file. If anything differs, the joined file would not play correctly, so the page lists the differences and offers re-encoding instead. Their lengths do not matter.
Re-encoding: size, fit and frame rate
Every frame is drawn at the output size you choose — clip 1’s size, the largest clip’s, or a 1080p, 720p, 480p, vertical or square preset — and encoded as H.264 with AAC sound in MP4, or VP9 with Opus in WebM. Clips of another shape are either fitted inside the frame with black bars, or scaled up to fill it with their edges cropped. All sound is converted to 48 kHz stereo, so clips recorded at 44.1 kHz or in mono join cleanly; clips without sound get silence so the picture and sound stay in step.
Crossfades, gaps and volume
A crossfade overlaps the end of one clip with the start of the next and blends the pictures; the sound uses an equal-power fade, so the level does not dip in the middle. Each clip must be at least twice as long as the crossfade. A gap puts black and silence between clips. Even out the volume measures each clip’s integrated loudness with ITU-R BS.1770 K-weighting and gating, then sets every clip to the clips’ median loudness, turning clips up by at most 15 dB and never past a sample peak of about −0.2 dBFS (a clip that cannot go further is marked “limited”). With a lossless join, only the audio is re-encoded for this; the picture is still copied.
Limitations
- Each clip contributes its main video track and its main audio track; subtitles, chapters and extra audio tracks are not carried over.
- Joining without re-encoding can leave a few milliseconds of silence at each join, because AAC audio starts with a short encoder delay (priming).
- Re-encoding needs WebCodecs (current Chrome, Edge, Safari or desktop Firefox) and decoders for the clips’ codecs; HEVC needs hardware support in the browser. HDR clips are converted to standard dynamic range.
- Up to 50 clips at a time. Long or 4K clips take a while to re-encode on a phone; large results stay in memory unless you use “Save straight to a file” (Chrome or Edge on a computer).
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
Does merging reduce the quality?
Not when the clips can be joined without re-encoding: the data is copied unchanged. Re-encoding loses a little detail, like any export; choose Very high quality to keep the loss small.
Why can my clips not be joined without re-encoding?
Because their setups differ — the page lists each difference, such as another resolution, codec, sample rate or encoder setting. Re-encoding converts them all to one setup so they can play as one video.
How do I change the order of the clips?
Drag a clip by the handle on its left, or press its ↑ and ↓ buttons. With the handle focused, the arrow keys move the clip too.
Can I merge a vertical and a horizontal video?
Yes, with re-encoding. Choose an output size (for example 1080 × 1920 for vertical), then Fit to show each clip whole with black bars, or Fill to crop it to the frame.
Are my videos uploaded?
No. The clips are read, joined and encoded inside your browser; the result is saved straight to your device.