Free Online MP4 Converter
Convert MOV, MKV, AVI, WMV, FLV, WebM and 20+ video formats to MP4 right in your browser. MP4Web uses WebCodecs and FFmpeg.wasm so every conversion runs locally — no uploads, no signup, no watermark, and no file size limit.
How to Convert a Video to MP4 Online
Converting a video to MP4 with MP4Web takes seconds. Because everything runs in your browser, there is no upload wait and your file stays private.
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1
Open the converter
Click Convert Video to MP4 above to open the in-browser tool. No download or sign-up is required.
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2
Add your video
Drag and drop your file or browse for it. MOV, MKV, AVI, WMV, FLV, WebM, 3GP, MPEG and 20+ other formats are supported.
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3
Choose MP4 and quality
Select MP4 as the output format, pick a quality preset and optional resolution, then click Start conversion.
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4
Download your MP4
Preview the result and click Download. The converted MP4 is generated locally and saved straight to your device.
A Browser-Based MP4 Converter That Keeps Your Files Private
Most online converters upload your video to a remote server, process it, and send it back. MP4Web is different: it uses the browser's WebCodecs API together with FFmpeg compiled to WebAssembly, so your video is converted entirely on your own device.
Files never leave your device
No uploads, no cloud processing. Your video is read, converted and written back locally, so sensitive or private footage stays private.
Any format in, any format out
Convert MOV, MKV, AVI, WMV, FLV, WebM, ProRes and more to MP4. You can also output WebM, MOV, MKV, AVI or extract MP3 audio.
Fast dual-engine processing
MP4Web tries the hardware-accelerated WebCodecs path first, then falls back to a full FFmpeg.wasm engine for complex or exotic codecs.
Free with no limits
No account, no watermark, no daily quota and no file size cap. Use it as often as you need, on desktop or mobile.
Video Formats You Can Convert to MP4
MP4Web accepts the most common video containers and can remux or transcode them into MP4 (H.264 video + AAC audio) for maximum compatibility across phones, tablets, browsers and editors.
| Input format | Typical source | Converts to |
|---|---|---|
| MOV | Apple devices, QuickTime, cameras | MP4 |
| MKV (Matroska) | Downloads, screen captures | MP4 |
| AVI | Legacy video, older cameras | MP4 |
| WebM | Web recordings, VP8/VP9 | MP4 |
| WMV | Windows Media | MP4 |
| FLV | Older web video | MP4 |
| 3GP / 3G2 | Mobile video | MP4 |
| MPEG / MPG / TS | Broadcast, DVDs | MP4 |
| ProRes (MOV) | Professional editing | MP4 (via FFmpeg) |
| OGV | Open-source video | MP4 |
Output options: MP4 (default), WebM, MOV, MKV, AVI, or extract MP3 audio only.
How MP4Web Compares to Other Online Converters
The biggest difference is where the conversion happens. Here is how MP4Web's local-first approach stacks up against typical server-based converters.
| Feature | MP4Web | Typical online converter |
|---|---|---|
| Where files are processed | Your device (browser) | Remote server |
| File upload required | No | Yes |
| Privacy of sensitive video | Stays private | Uploaded to a third party |
| Account needed | No | Often yes |
| File size limits | None (device memory only) | Usually capped |
| Watermark on output | No | Sometimes |
| Cost | Free | Free tier + paid plans |
What Is an MP4 File and Why Convert to It?
MP4 (MPEG-4 Part 14, file extension .mp4) is the most widely supported video container. It usually wraps H.264 or H.265/HEVC video with AAC audio, which plays natively on virtually every phone, computer, browser and media player. Converting to MP4 is the safest way to make sure a video plays everywhere and shares cleanly across apps and platforms.
MP4Web outputs standard MP4 with H.264 video and AAC audio using the widely compatible yuv420p pixel format and +faststart (moov atom at the front), so your file starts playing instantly when streamed or embedded.
Frequently Asked Questions
How do I convert a video to MP4 online?
Click Convert Video to MP4, drop or browse for your file, pick MP4 as the output and click Start. The conversion runs in your browser and you can download the MP4 immediately — no upload step involved.
Is this MP4 converter free and safe?
Yes. MP4Web is 100% free with no signup or watermark. Because every conversion happens locally using WebCodecs and FFmpeg.wasm, your files never leave your device, which is inherently safer than tools that upload videos to remote servers.
What video formats can I convert to MP4?
You can convert MOV, MKV, AVI, WMV, FLV, WebM, 3GP, MPEG, TS, MTS, M2V, OGV and many other formats to MP4. MP4Web can also output WebM, MOV, MKV, AVI, or extract MP3 audio from a video.
Are my files uploaded to a server?
No. MP4Web processes every file locally in your browser. There is no upload step, so your videos stay private on your device and are never stored on or seen by a remote server.
Is there a file size or time limit?
There is no artificial limit. The only constraint is your device's available memory, since the converted file is assembled in the browser. For very large videos, closing other tabs helps.
Does MP4Web work on mobile?
Yes. MP4Web runs in any modern mobile or desktop browser that supports WebAssembly and (for the fast path) WebCodecs. If WebCodecs isn't available, the FFmpeg.wasm fallback handles the conversion instead.