Video Converter
Video converter for MP4, MOV, MKV and WebM. Every target says up front whether it repackages the clip or re-encodes it.
Runs entirely in your browser — your files and text never leave your device.
Drag & drop your file here, or
Instant means the file is repackaged with no quality loss; re-encode converts the video on your device.
Load a clip and the containers it can move into appear here, each tagged instant or re-encode for the codec your browser will use.
Working on your device — keep this tab open until it finishes.
How to use
- Drop the clip onto the Video field, or use Choose file if dragging is awkward.
- Wait for the Source line to appear under the preview. It names the container, the codec and the pixel dimensions it read out of the file.
- Pick a target under Convert to. Only the three containers you are not already using get listed.
- Read the tag on that button before committing. Instant repackages the existing video track; re-encode pushes every frame back through the encoder.
- Press Convert and leave the tab open. The bar fills as frames go through.
- Play the result in the lower player. Check the sound came along, especially on a WebM, since that container takes Opus rather than AAC.
- Hit Download. The file saves as converted.mp4, converted.mov, converted.mkv or converted.webm, matching whichever target you chose.
About this tool
Most “this video won't play” problems are container problems. The footage is fine. The wrapper around it is something the phone, the editor or the website refuses to open. Load the clip into the video converter and it reports what it found in a line under the player, something like Source: MOV · H.264 · 1920×1080. The three containers you aren't already in then appear as buttons, each carrying a tag. Instant means the video track can be copied straight across; re-encode means every frame gets decoded and encoded again.
The work is done by WebCodecs, the same video engine your device uses for its own camera, driven by the mediabunny library. A re-encode is therefore as fast as your hardware and no faster: a two-minute 4K clip takes real time on a laptop and longer on a phone. While it runs you get a progress bar and a Cancel button, and the finished file appears in a second player you can scrub through before deciding to keep it.
One screen recording, two very different targets
A three-minute macOS screen recording lands as a MOV around 60 MB, H.264 inside. The Source line reads MOV · H.264 · 1920×1080, and the MP4 button carries the Instant tag: the same frames move into the new wrapper untouched, the bar sweeps past in a moment, and the file that comes out is the size that went in.
Send the identical clip to WebM instead and the tag flips to re-encode. Every frame goes back through the encoder on its way to VP9, the audio becomes Opus, and three minutes of footage takes real time to chew through. Same clip, same page, and the tags told you the cost difference before you pressed anything.
Rough edges
- Instant is narrower than the container spec allows. Each tag is worked out from the codec this browser will actually ask that container for (H.264 for MP4, MOV and MKV, VP9 for WebM), so an iPhone clip in HEVC reads re-encode even though an MP4 could legally carry HEVC untouched. H.264 sources moving into MP4, MOV or MKV are the genuinely instant case.
- Four containers come out: MP4, MOV, MKV, WebM. AVI, WMV and FLV cannot be written from a page like this, so they are absent rather than hidden behind a warning.
- The whole output is assembled in memory before it is handed over, and MP4 and MOV are built that way deliberately so the index sits at the front of the file. A phone converting a long 4K recording can run out of room and fail late in the job.
Frequently asked questions
What can I load into it?
Anything your device can decode as video, which covers the usual phone and camera output as well as the four containers it writes. If the file cannot be read you get a message saying the format could not be opened.
Will converting to MP4 make the file smaller?
Not by design. A repackage keeps the same video data, so the size barely moves, and a re-encode aims at quality rather than a size target. The Video Compressor is the one with the size dial on it.
Does the audio survive the conversion?
It carries over, sometimes re-encoded on the way. MP4 and MOV get AAC; WebM and MKV get Opus. A clip that arrived silent stays silent, since no track is invented for it.
What does Cancel actually do mid-run?
It abandons the conversion on the spot. No partial file is offered, the source clip stays loaded with its Source line intact, and the targets are ready for another go, so backing out of an accidental re-encode costs nothing.
Can I queue up a folder of clips?
One clip at a time. The page holds a single source and reports on that file alone, so a batch means converting them one after another. Repackages are quick enough that the queue mostly costs clicks rather than waiting.
Why is the Convert button greyed out?
It stays disabled until a file has loaded, and it stays disabled for good if the browser has no WebCodecs support at all. A warning at the top of the page says so and names what does work: Chrome, Edge, or a recent Safari or Firefox on desktop.
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