Video Converter Online Free
Convert MP4, WebM, MOV, AVI, MKV, FLV, and 13 other formats. For compatible containers, a fast lossless remux takes seconds. Full re-encoding with resolution and quality controls is available when you need to change codecs. All processing runs in your browser.
Video format problems come up constantly. A GoPro saves MKV files that won't upload to Instagram. An iPhone records MOV that a Windows PC won't open properly. A 4K walkthrough video is 2GB when a client only needs a 720p version they can open on their phone. The right converter makes these problems quick to solve.
This free online video converter supports 13 output formats including MP4, WebM, MOV, AVI, and MKV. For containers that share the same codec, a fast lossless remux takes seconds without touching the video data at all. Full re-encoding lets you change resolution and quality when you actually need to reduce file size or switch codecs. Everything runs in your browser using FFmpeg compiled to WebAssembly — no uploads, no software.
How to Convert Video Online
- 1Upload your video file by dragging it into the box or clicking Select Files.
- 2Pick the output format from the grid. Options include MP4, WebM, MOV, AVI, MKV, FLV, and more.
- 3If a fast remux is possible, the tool suggests it. Accept for an instant lossless conversion or switch to Re-encode for quality and resolution controls.
- 4In re-encode mode, set your target resolution (original, 1080p, 720p, 480p, 360p) and adjust the CRF quality slider.
- 5Click Convert. The first run downloads the FFmpeg engine (about 30MB) once.
- 6Preview the output video and download when ready.
When to Use This Tool
- Converting MKV to MP4 for devices that don't support MKV containers
- Changing MOV files from iPhone or GoPro to a universally compatible format
- Preparing video for web publishing in WebM or MP4 format
- Reducing video resolution from 4K to 1080p or 720p to save space
- Converting legacy AVI or FLV files to modern formats
- Remuxing without re-encoding to change container format in seconds
Real World Examples
Converting a GoPro MKV to MP4 for sharing
A travel photographer shoots 4K footage on a GoPro that outputs MKV files. Uploading to social media requires MP4. Since both formats can share the same H.264 video stream, the converter detects this and offers a fast remux. The 2GB file converts in under 10 seconds with no quality loss.
Downscaling a 4K recording for email
A real estate agent records a 4K property walkthrough (1.8GB). He needs a smaller version to send to clients. Selecting 720p resolution and MP4 output at CRF 26 produces a 180MB file that streams smoothly on any phone.
Preparing video for a website
A developer needs to add a background video to a landing page. The source MOV file is 450MB. Converting to WebM (VP9) at 720p reduces it to under 20MB while keeping excellent quality for web playback.
Benefits of This Video Converter
- Supports 13 output formats: MP4, WebM, MOV, AVI, MKV, FLV, 3GP, MPEG, M4V, OGV, MXF, AV1, YUV
- Fast remux mode: near-instant lossless container swap when codec is compatible
- Full re-encode mode with resolution downscaling (1080p to 360p) and CRF quality control
- Video preview after conversion — watch before downloading
- No software needed — runs entirely in your browser via WebAssembly
- Files never uploaded to any server — complete privacy
- Free with no account or usage limits
Supported Video Formats
| Format | Input | Output | Notes |
|---|---|---|---|
| MP4 (H.264) | Yes | Yes | Best overall compatibility |
| WebM (VP9) | Yes | Yes | Best for web use |
| MOV | Yes | Yes | Same as MP4 internally |
| AVI | Yes | Yes | Legacy Windows format |
| MKV | Yes | Yes | Fast remux available |
| FLV | Yes | Yes | Legacy Flash format |
| AV1 | Yes | Slow | Very CPU-heavy — consider VP9 instead |
| WMV | Yes | No | Input only — WMV codec not in browser build |
| AVCHD | Yes | No | Camera input format only |
| SVI | No | No | Samsung proprietary — no free tooling |
Tips for Best Results
- Use fast remux when the source already has H.264 video and you just need a different container. It's instant and lossless.
- CRF 18 to 23 gives near-lossless quality for MP4 output. Higher values (28 to 35) produce smaller files with visible quality reduction.
- WebM (VP9) gives about 30 to 50% better compression than MP4 at the same quality — good for web video.
- Avoid AV1 output for anything over 5 minutes. Even on a fast computer, encoding is extremely slow in WebAssembly.
- Files over 500MB may strain the browser. For large files, using desktop FFmpeg is faster and more stable.
- The browser caches the FFmpeg WASM engine after the first load. Revisiting the page doesn't require another 30MB download.
Frequently Asked Questions
What is the difference between remux and re-encode?
Remux just copies the video and audio streams into a different container without touching the actual data. It's instant and lossless. Re-encode decodes the video and re-encodes it with new settings — useful for changing codecs, resolution, or quality, but much slower.
Is this video converter free?
Yes. No accounts, no payments, no limits. The tool uses FFmpeg compiled to WebAssembly, which runs entirely in your browser.
Can I convert 4K video files?
Yes, but large 4K files are slow to process in a browser. A 5-minute 4K video may take 10 to 30 minutes depending on your device. Keep the tab active during conversion.
Are my video files uploaded to any server?
No. All conversion happens locally in your browser using WebAssembly. Your files never leave your device.
Why does the first conversion take longer to start?
The first time you use the converter, your browser downloads the FFmpeg WebAssembly binary (about 30MB). It caches this automatically, so future conversions start right away.
Which format should I use for web video?
MP4 (H.264) works everywhere and is the safest choice. WebM (VP9) gives better compression but requires a modern browser. For a website's background video, WebM with an MP4 fallback is ideal.
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Conclusion
This free online video converter handles the most common video conversion tasks directly in your browser. Fast remux makes simple container changes instant and lossless. Full re-encoding gives you control over resolution and quality when you need to change codecs or reduce file size. No uploads, no accounts, no software. Use the tool above to start converting your video files now.