Video Joiner
Combine multiple video clips into one, or add audio to a video — entirely in your browser. No upload, no account, completely private.
Drop videos here
or click to add files
MP4, MOV, AVI, MKV, WebM, WMV and more · multiple files supported
Join Settings
Join Method
Free Online Video Joiner — Merge Video Clips in Your Browser
Zolkit's Video Joiner uses FFmpeg WebAssembly to combine video clips and merge audio with video entirely in your browser. Upload multiple MP4, MOV, AVI, MKV, or WebM files, arrange them in order, and join them into a single MP4 — without uploading a single byte to a server. Quick Join copies streams without re-encoding for near-instant results with same-format clips. Smart Join re-encodes with H.264 to handle clips from different cameras, resolutions, and codecs. The Add Audio tab lets you replace or mix an audio track into any video file. All processing runs locally on your device.
100% Private
Your videos never leave your device. All processing runs in WebAssembly inside the browser tab — no server, no cloud, no data retention.
Join Any Clips
Quick Join copies streams for near-instant merging of same-format clips. Smart Join re-encodes with H.264 to handle clips from different devices and resolutions.
Drag to Reorder
Arrange clips in any order by dragging. See filenames and sizes at a glance. Remove any clip before processing.
Add Audio to Video
Replace a video's audio track with music or a voiceover, or mix the new audio with the original. Supports MP3, AAC, WAV, FLAC, and OGG.
FFmpeg-Powered
Uses FFmpeg's concat demuxer for copy mode and filter_complex concat for re-encode mode — the industry standard for video joining.
Free, No Account
No subscription, no sign-up, no watermark, no file count limit. Zolkit's Video Joiner is completely free.
How to Merge Video Clips Online
- 1
Click 'Join Videos' tab, then drop your video files onto the upload zone or click to select multiple files. Files are listed in join order.
- 2
Drag clips to reorder them. Choose Quick Join (for clips from the same device/camera) or Smart Join (for clips from different sources). Set quality and resolution if using Smart Join.
- 3
Click 'Join Videos', wait for processing, then download the merged MP4. For adding audio, switch to the 'Add Audio to Video' tab and upload one video plus one audio file.
Frequently Asked Questions
Is my video private when I merge clips online?
Yes. Zolkit's Video Joiner processes everything inside your browser using WebAssembly. Your files are never uploaded to a server. The video engine (~30 MB) is downloaded once and cached locally — after that, all joining works completely offline.
What's the difference between Quick Join and Smart Join?
Quick Join uses FFmpeg's concat demuxer to copy video and audio streams without re-encoding. It's nearly instant regardless of file size, but requires all clips to have the same codec, resolution, and frame rate. If clips are from the same phone (all H.264 or all HEVC), Quick Join works perfectly. Smart Join re-encodes everything to H.264 MP4, handling any combination of codecs, resolutions, and frame rates — at the cost of processing time.
Can I merge videos from different phones or cameras?
Yes, use Smart Join. Clips from different devices often have different codecs (H.264 vs HEVC), resolutions (4K vs 1080p), or frame rates (30fps vs 60fps). Smart Join normalizes all clips to a common resolution and re-encodes them to H.264, producing a seamlessly merged output. Set the output resolution to the lowest resolution of your clips to avoid upscaling.
How many clips can I join at once?
There is no enforced limit on clip count. The practical limit is your device's available RAM — each clip is loaded into memory during processing. Most modern computers handle 10–20 clips without issues. For very large collections, consider joining clips in batches of 5–10 and then joining the resulting files.
How do I add background music to a video?
Switch to the 'Add Audio to Video' tab. Upload your video file and your music file (MP3, AAC, WAV, etc.). Choose 'Replace audio' to remove the original audio and use only the music, or 'Mix audio' to blend the original audio (speech, ambient sound) with the new music. The output always ends at the shorter of the two files.
What formats are supported?
Video input: MP4, MOV, AVI, MKV, WebM, WMV, M4V, FLV, and most other common formats. Audio input: MP3, AAC, WAV, FLAC, OGG, M4A. The output is always H.264-encoded MP4, which plays on every device and platform.