Video Converter
A video converter that re-encodes MP4, MOV, MKV, WEBM, AVI, FLV and other files into MP4, WEBM, MKV, MOV or AVI. It runs on an in-browser engine downloaded once and cached afterwards.
Convert between MP4, WEBM, MOV, MKV and AVI.
How to use Video Converter
- Upload a video file from your device
- Pick the target format: MP4, WEBM, MOV, MKV, or AVI
- Convert and download the re-encoded video
About Video Converter
Video Converter runs a WebAssembly build of ffmpeg directly on the page. The first time you use it, the browser fetches the roughly 32 MB engine once and caches it; from then on, converting is just picking a target format and clicking Convert. It accepts MP4, MOV, MKV, WEBM, AVI, M4V, 3GP, FLV, WMV and TS going in, and writes one of five containers coming out, each paired with the codec that container expects: MP4, MOV and MKV carry H.264 video at CRF 23 with 160 kbps AAC audio, WEBM uses VP9 with Opus, and AVI uses MPEG-4 with MP3. MP4 files also get the faststart flag so they can begin playing before the whole file has downloaded.
Most people arrive with a screen recording saved as .mov or .webm that a client, a course platform or an older TV refuses to open — convert it to MP4 and it plays almost everywhere. The same path handles WEBM to MP4, MKV to MP4, AVI to MP4 or MP4 to WEBM for the web. Width, height and frame rate pass through untouched; only the codec and container change. Every output is a video file, so this is not the tool for pulling a soundtrack out as a standalone MP3.
Encoding is single-threaded, so expect roughly real-time speed, with VP9 WEBM slower still; a two-minute 1080p clip is easy, while a two-hour 4K file will likely run the browser out of memory. Each pass is a fresh re-encode, so convert from the original to avoid stacking quality loss. The file never leaves your device — everything runs in your browser and the result is handed straight back as a download.
Frequently asked questions
- Which formats can I convert to and from?
- Input: MP4, MOV, MKV, WEBM, AVI, M4V, 3GP, FLV, WMV, TS and anything else your browser labels as video. Output: MP4 (H.264), WEBM (VP9), MOV (H.264), MKV (H.264) or AVI (MPEG-4).
- How do I convert MOV to MP4?
- Choose the .mov file, leave the target on MP4 (the default), and click Convert. The result uses H.264 video and AAC audio, which plays on Windows, Android, smart TVs and every browser.
- How do I convert WEBM, MKV or AVI to MP4?
- Pick the file, leave the target on MP4, and click Convert. Whether the source is WEBM, MKV, AVI, FLV, WMV or another format your browser can read, the output is the same H.264/AAC MP4 that opens almost everywhere.
- Can I convert a video to MP3?
- No. This tool outputs video files, and each one keeps the picture and sound together in a single container. To get just the audio as an MP3, use a dedicated audio-extraction tool instead; this converter is for changing the video format, not stripping out the soundtrack.
- Does converting reduce quality?
- Slightly. Every conversion re-encodes the video, so some detail is lost. The H.264 setting (CRF 23) is the standard visually-good default; converting the same file repeatedly compounds the loss, so convert from the original each time.
- Why is it slow?
- The encoder runs on a single CPU thread inside your browser, so expect roughly real-time speed for H.264 and slower for VP9 WEBM. A progress bar shows how far along the encode is.
- Is there a file-size limit?
- No fixed limit, but the whole file plus the output must fit in browser memory. Clips of a few minutes convert reliably; multi-gigabyte files often fail. Trim or compress the video first if it is very large.
- Can it convert 4K video?
- It can, but 4K files are heavy: the whole clip has to fit in browser memory while it encodes, so a short 4K clip converts fine while a long one may run out of memory and fail. For big 4K files, trim them or drop the resolution first.
- Will the resolution or frame rate change?
- No. Width, height and frame rate are passed through unchanged. Use the Resize Video tool if you want a smaller resolution.
- Why does the first conversion take longer?
- The page has to fetch the ~32 MB ffmpeg engine once. It is cached by the browser, so later conversions in the same browser skip the download.
- What happens to the audio?
- Audio is re-encoded to match the container: AAC at 160 kbps for MP4, MOV and MKV; Opus for WEBM; MP3 for AVI. One video track and one audio track are kept.
- Does it work on my phone?
- Yes, in a modern mobile browser, but phones have far less memory than laptops, so keep files short. Long recordings may fail with an error rather than crash the tab.
- Is this video converter free?
- Yes. It is completely free with no account, no watermark and no upload. Everything runs in your browser, so there is nothing to install and nothing to pay for.
- Is my video uploaded to a server for conversion?
- No. The ffmpeg engine runs in your browser, the file is read from your device into memory, and the converted result is offered back as a download.