Video Concatenator

How to join video clips online

1. Drop or pick 2 to 10 video files. MP4, WebM, MOV and MKV are accepted; combined size up to 500 MB. The upload travels over HTTPS to our EU-located processing server.
2. Reorder the list. Each clip in the queue has Up and Down buttons; press them to put the clips in the exact playback order you want.
3. Press Join clips. The job enters our BullMQ queue. The server checks whether every input shares the same codec, frame size and frame rate. If yes, FFmpeg's concat demuxer stream-copies all clips without re-encoding (lossless and fast). If no, FFmpeg falls back to a re-encode pass that normalises everything to H.264 + AAC before joining.
4. Download the joined video. A signed URL appears when the job finishes. All source clips and the produced output are auto-deleted from disk within 15 minutes.

What this tool does

This is a free video concatenator that stitches 2 to 10 clips together end-to-end into a single MP4. Joining videos is a workhorse edit for short-form: producing a TikTok or Reel from multiple takes, splicing intro and outro clips onto a long-form video, building a compilation, or assembling a boomerang loop (forward clip + reversed clip). We run the join server-side with FFmpeg so the page works in any modern browser - no SharedArrayBuffer, no cross-origin-isolation, no client-side ffmpeg.wasm.

Why join videos in the browser

An online merge videos online tool earns its keep when you want a single quick join without installing a desktop editor. CapCut, Premiere, DaVinci Resolve and iMovie all support concatenation but each is overkill if the inputs already match and you just need them stitched. The catch with most online services is unclear retention - your uploads might sit on someone else's server for weeks. Our retention policy is strict and automatic:

• All uploaded clips and the joined output are auto-deleted within 15 minutes on EU servers.
• The signed download URL expires alongside the file - it is not a permanent public URL.
• Nothing about the file content is logged or analysed.

How the join works under the hood

FFmpeg ships two concatenation strategies and the tool picks the right one automatically:

• Concat demuxer (-f concat -i list.txt -c copy) - the fastest path. FFmpeg reads a manifest of clip paths and stream-copies packets from each clip into the output container. This requires every clip to use the same codec, frame size, frame rate and audio settings; if anything differs the demuxer fails or produces a glitched output. We probe each clip with ffprobe before choosing this path.
• Concat filter (-filter_complex concat=n=N:v=1:a=1) - the safe fallback. Every clip is decoded, normalised to H.264 + AAC, then encoded into a single MP4. This is dramatically slower (a full re-encode) but works for mixed sources. We always use the concat filter when any clip differs from the first in codec, resolution or frame rate.

If you want a guaranteed lossless join, make sure all your clips share the same parameters before uploading - run them through the video converter first to normalise to MP4 + H.264 + AAC if they do not. That extra pass is cheap and makes the join itself lossless.

Use cases for the free video concatenator

• Creators - assemble a multi-take Reel or TikTok from several short clips without launching CapCut.
• Engineers - splice an intro clip onto a screen recording before sharing it in a PR description or sprint review.
• Marketers - chain product clips into a 30-second highlight reel for paid social.
• Educators - join lecture segments into one downloadable file for LMS upload (Moodle, Canvas, Blackboard).
• Sports fans - build a highlight compilation from individual play clips.
• Boomerang loops - trim a clip, reverse it with the video reverser, then join the forward and reversed clips to produce a seamless ping-pong loop.

Common pitfalls

• Mismatched frame rates produce jank. If clip A is 30 fps and clip B is 24 fps the concat filter normalises them, but the cadence change at the boundary can look subtle off. Convert both to the same fps first for the smoothest result.
• Mismatched resolutions trigger letterboxing. When clips differ in size the filter resizes everything to the largest input; smaller clips end up scaled with padding. Crop or convert before joining for best results.
• Audio sync can drift if any clip has variable frame rate (common with screen recordings). The re-encode pass forces constant frame rate, but very pathological VFR inputs may still produce a small drift.
• The 500 MB combined cap is shared across every clip in the batch. If your inputs are bigger than that, compress them first with the video compressor or split the job into smaller batches.
• No transitions. The concatenator does pure end-to-end joins. If you want fades, pre-render fade-in and fade-out clips and include them as part of the queue.

Privacy and browser support

The tool works in any modern browser that can upload a file - recent Chrome, Edge, Firefox, Safari and mobile equivalents. There are no SharedArrayBuffer or cross-origin-isolation requirements. All uploaded clips travel over HTTPS to our EU-located processing server, are joined with FFmpeg, and are made available as a single signed, time-limited download URL. After 15 minutes every input and the output are deleted from disk and the signed URL stops working. Nothing about your file content is logged or analysed.