Video Stream Copy
Losslessly remux between MP4, MKV, MOV and WebM containers without re-encoding. Zero loss in video and audio quality, dozens of times faster than regular transcoding. Processed entirely in your browser for privacy and security.
Zero Quality Loss
Video and audio streams are copied as-is with no re-encoding, keeping the quality identical to the source file
Blazing Fast
No decoding or encoding needed—only the container shell is swapped, so processing is dozens of times faster than regular transcoding and finishes in seconds
Privacy Protection
All processing happens locally in your browser; your video files are never uploaded to any server, fully protecting your privacy
Drag and drop video files here
or
Supports MP4, WebM, MOV, MKV, AVI, and more
Stream Copy Your Video in Three Steps
Upload Your Video
Click the upload area or drag in a video file, and the tool automatically reads the source container format and codec information
Choose the Target Container
Pick a target format among MP4, MKV, MOV and WebM, and the tool marks which ones can be remuxed losslessly
Stream Copy and Download
Click to start the stream copy, which finishes in seconds, then download your new container file with zero quality loss
Typical Use Cases for Video Stream Copy
Losslessly Convert MKV to MP4
Many HD videos are packaged as MKV but are actually H.264 inside. Use stream copy to turn MKV into MP4 with no quality change in seconds, so it plays directly on phones and TVs without a lengthy re-encode.
Fix Extensions and Compatibility
Some platforms or players only accept a specific container extension. When the video codec itself is compatible, use stream copy to turn MOV into MP4, MP4 into MKV and so on—just swapping the shell resolves "unsupported format" errors without sacrificing quality.
Quickly Rewrap Editing Footage
When your editing software handles a certain container poorly but has no issue with its codec, use stream copy to switch containers quickly, avoiding the quality loss and long waits of re-encoding so your footage imports smoothly onto the timeline.
Batch Rewrap for Archiving
When organizing a media library, you may want to unify videos from different sources into one container format without losing quality. As long as the codec is compatible, stream copy is the fastest and most faithful choice, finishing a file in seconds.
Codec and Container Compatibility Table
| Container Format | Supported Video Codecs | Supported Audio Codecs |
|---|---|---|
| MP4 | H.264, H.265/HEVC, AV1, VP9 | AAC, MP3, Opus |
| MOV | H.264, H.265/HEVC, AV1 | AAC, MP3 |
| MKV | Nearly all codecs (H.264, H.265, VP9, AV1, etc.) | Nearly all codecs (AAC, Opus, MP3, FLAC, etc.) |
| WebM | VP8, VP9, AV1 | Opus, Vorbis |
Note: The actually available target formats depend on your uploaded file's real codec; the tool automatically marks the losslessly remuxable options after reading the source file.
Features
- Losslessly remux between MP4, MKV, MOV and WebM
- No re-encoding at all, zero loss in video and audio quality
- Automatically detects the source codec and marks the available target formats
- Blazing fast processing, finished in seconds
- Supports video files up to 2GB
- All processing in the browser — files never leave your device
- Completely free, no account required
Technical Notes
The VideoKit stream copy tool reads the already-encoded video and audio packets directly from your source file and writes them untouched into a new container format, never passing through a decoder or encoder. This works on the same principle as FFmpeg's -c copy option, guaranteeing lossless quality and delivering extremely high processing speed.
After upload, the tool automatically analyzes the source file's codec and only allows target containers that can natively hold that codec, fundamentally preventing the mistake of a "remux" that is actually a re-encode. All processing happens locally in your browser, and the server handles none of your video data.
Frequently Asked Questions
What is Stream Copy?
Stream copy, also called remuxing, moves video and audio streams from one container to another without decoding or re-encoding. There is zero loss in video and audio quality, and it is dozens of times faster than transcoding—the equivalent of FFmpeg's -c copy.
How is stream copy different from regular format conversion?
Regular conversion re-encodes and can change the resolution, bitrate or codec, but with quality loss and more slowly. Stream copy only swaps the container shell and leaves the encoded data untouched, so it is lossless and lightning fast, but it requires the target container to support the source video's codec.
Why are some target formats unavailable?
Stream copy requires the target container to natively hold the source codec. For example, H.264 cannot go into WebM. When incompatible, the tool automatically disables that option and marks it as "re-encoding required"; in that case, please use the Video Format Converter instead.
Does stream copy change the file size?
Barely. The video and audio data are copied as-is, with only minor differences in container overhead, so the total size stays almost identical to the source file.
Are subtitles and multiple audio tracks preserved?
The tool copies the main video track and the main audio track; external subtitle tracks are not written to the output. To fully preserve every track, we recommend a professional desktop tool.
What are the common codec and container compatibilities?
H.264 video is well suited for stream copy between MP4/MOV/MKV; VP9 video works well between WebM/MKV; MKV offers the broadest compatibility and can hold nearly any codec. The exact options depend on your uploaded file's real codec.
Will my files be uploaded to a server?
No. All processing is done locally in your browser. Your video never leaves your device.
How large a video file is supported?
Video files up to 2GB are supported. Stream copy requires no decoding or re-encoding, so memory usage is low and processing is lightning fast—even large HD videos finish quickly.