Drag & Drop or click to select Video M4S
Supports .m4s or separated mp4 video tracks
Drag & Drop or click to select Audio M4S
Supports .m4s, .m4a, or aac audio tracks
Processing Logs & Progress
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// Waiting for files or URLs input...
Merged Video Preview
Download MP4No Video Loaded Yet
Provide video.m4s and audio.m4s files on the left and click "Merge Tracks" to generate standard MP4.
How it works
Platform streams (such as Bilibili, Xiaohongshu, etc.) split media into separate .m4s video and audio fragments. This application uses WebAssembly to execute FFmpeg directly inside your browser—stitching the streams together with -c copy for zero quality loss in seconds.