CanDoYa
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Free Video Converter

Runs entirely in your browser - no upload, no sign-up.

Choose a video to convert between MP4, WebM, MOV, and MKV

Your source and converted video stay in this browser tab. The video is never uploaded.

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What does a video converter do?

A video converter changes a video's container and codecs so it works with a different player, device, editor, or website. Choose a local file, select MP4, WebM, MOV, or MKV, and download the re-encoded result. Processing runs in your browser, so the source is not uploaded.

How to use

  1. 1Choose a video. Drop an MP4, WebM, MOV, MKV, AVI, MPEG, or another common video file into the converter.
  2. 2Pick the output format. Select MP4, WebM, MOV, or MKV. Keep the source resolution for a format-only conversion, or set a lower limit.
  3. 3Convert in your browser. Start the conversion and keep this tab open while the local video engine decodes and re-encodes the file.
  4. 4Preview and download. Check the result when the browser supports its container, then download the converted video to your device.

Who it's for

This converter loads a WebAssembly build of FFmpeg only after you start a conversion. MP4 and MOV use H.264 video with AAC audio. WebM uses VP8 with Opus. MKV uses H.264 with AAC. VP8 keeps WebM encoding practical when the browser must use the single-thread fallback, while the other combinations favor broad playback support.

Conversion creates a new, lossy encode. The main video stream and optional audio stream are kept, while subtitles, chapters, attachments, and source metadata are left out. Browser memory and processor speed make this tool best for short or moderate files. Large, damaged, encrypted, or unusual professional formats may need a desktop converter.

FAQ

Is my video uploaded when I convert it?

No. Your selected video is read from a browser file object and processed by a WebAssembly video engine in this tab. The engine code downloads on first use, but the source and result are not sent to that server or stored in a CanDoYa account.

Is this online video converter free?

Yes. You can convert and download video without an account, subscription, credit limit, or watermark. Practical limits come from browser memory and processing speed. The tool applies a conservative file limit from 100 MB on mobile or lower-memory devices to 500 MB on high-memory desktops.

Which video formats can I convert?

The tool accepts common inputs including MP4, WebM, MOV, MKV, AVI, MPEG, WMV, MTS, and several related containers. It outputs MP4, WebM, MOV, or MKV. A listed container can still contain an unusual codec that this WebAssembly build cannot decode, so no browser converter can guarantee every file.

Should I convert video to MP4, WebM, MOV, or MKV?

Choose MP4 for broad support across phones, browsers, presentation apps, and messaging tools. Choose WebM for VP8 and Opus playback on the web. MOV fits many Apple and editing workflows. MKV is a flexible container, but browser playback is less consistent, so a desktop media player may be needed.

Why can I convert a video that the browser cannot preview?

The browser's built-in video element and the FFmpeg conversion engine do not support exactly the same containers and codecs. A MOV or MKV source may fail in the preview yet still decode in FFmpeg. The converter therefore keeps the file available and lets you try instead of treating preview failure as proof that conversion is impossible.

Does video conversion reduce quality?

Usually. This tool re-encodes video so each output uses a predictable codec and container combination. Higher quality keeps more visible detail but usually creates a larger file. Balanced is a useful starting point. Keeping source dimensions avoids deliberate downscaling, but re-encoding is still not mathematically lossless.

Are subtitles and metadata preserved?

No. The output includes the first video stream and, unless you remove it, the first available audio stream. Subtitles, chapters, attachments, GPS data, camera tags, and other source metadata are not copied. Use a desktop media tool when those extra streams or tags must be retained.

Why is browser video conversion slow or unsuccessful?

Every frame must be decoded and encoded on your device, and the source plus output can occupy memory at the same time. Long 4K footage, unusual codecs, damaged files, and low-memory phones are the hardest cases. Keep the tab open, close other heavy tabs, or use desktop software for large projects.