Video merge — concat multiple clips into one (same codec)
Concatenate multiple video files via the ffmpeg.wasm concat demuxer. Reorder by drag. Stream copy keeps the codec untouched, but all inputs must share the same codec / resolution / frame rate (great for stitching segments produced by the video cut tool).
How to use
Drop two or more videos to add them to the list. Drag entries to reorder, then click Merge — ffmpeg.wasm's concat demuxer joins them into one file. Stream copy preserves the codec, but all inputs must share the same codec, resolution, frame rate and pixel format (great for stitching outputs from the video cut tool).
FAQ
- Are videos uploaded?
- No. ffmpeg.wasm runs inside your browser; videos never leave your device.
- Why does merging fail?
- The concat demuxer requires matching codecs, resolutions and frame rates. Pre-process with the video resize or video convert tool first.
- Can I mix videos with and without audio?
- No, the track layout must match. Use the video mute tool to bring all inputs to the same track structure first.
- How long is the output?
- The sum of the inputs. Playback is seamless, though there can be a brief hiccup at the keyframe join points.
Related tools
Video cut — trim by range with stream copy, no quality loss
Trim a video to a chosen range with ffmpeg.wasm using stream copy — no re-encoding, no quality loss, original codec and extension preserved. Cut points snap to the nearest keyframe so the start may shift slightly. Supports batch processing and a single ZIP download.
Video format convert — MP4 / MOV / WebM stream copy
Change the video container (e.g. mov → mp4) without re-encoding by using ffmpeg.wasm stream copy. Works for codec-compatible combinations only. Supports batch processing and a single ZIP download.
GIF to MP4 converter — H.264 cuts file size to 1/5–1/10
Convert animated GIFs to H.264/AAC MP4 videos. GIFs balloon quickly; MP4 (H.264) typically shrinks the file to 1/5–1/10 the size and plays inline on X (Twitter), Bluesky, Discord and other social platforms. ffmpeg.wasm runs entirely in your browser — GIFs never leave your device. Supports batch processing and a single ZIP download.
Subtitle Converter
Convert subtitle files between SRT / VTT / ASS / SSA / SBV / SUB / SMI / LRC. Drop files and pick a target format — runs entirely in your browser via subsrt-ts (MIT). No uploads.