ASF to MP4 converter
Convert ASF to MP4 in seconds, free and unlimited. No upload, no sign-up, no watermark: your video never leaves your device.
Last updated
Quick answer: To convert ASF to MP4, add the ASF file to the iHateFiles ASF to MP4 converter and press Convert. The conversion runs in your browser, so the file is never uploaded, and it is free with no sign-up, watermark or size limit. ASF is a format most software has stopped opening. MP4 is not.
Should you convert ASF to MP4?
Yes, if the ASF will not play where you need it. MP4 with H.264 plays on essentially everything, which is why nearly every other video format is converted to it.
The picture is re-encoded
An ASF usually holds Windows Media video and audio. This writes H.264 video with AAC sound into the MP4. Both sides are compressed with loss, so this is a second generation: leave the quality at its default or higher, because the encoder is working from ASF artefacts rather than the original.
Expect a smaller MP4
H.264 video is a much more efficient codec than what an ASF holds, so at the same visual quality the MP4 is usually a third to a half of the size.
Where the MP4 will play
MP4 plays on every phone, laptop, TV, browser and messaging app.
ASF and MP4 side by side
| ASF | MP4 | |
|---|---|---|
| Inside the file | Windows Media video and audio | H.264 video with AAC sound |
| Compression | Lossy | Lossy |
| Carries sound | Yes | Yes |
| Plays on | Needs converting first | every phone, laptop, TV, browser and messaging app |
| Here | Read only | Read and write |
What usually goes wrong
About the ASF. ASF, WMV and WMA all share the same file signature, so identifying which one you have means looking at the streams inside rather than the first few bytes.
About the MP4. Two MP4 files can behave completely differently depending on the codecs inside. A file that will not play is usually an unusual codec in an ordinary container, not a broken file.
How to convert ASF to MP4
- Add your ASF file. It is read from your disk and stays there.
- Check the settings. The output format is already set to MP4.
- Press convert and the MP4 file is saved back to your device.
MP4 converter: everything that converts to MP4
Questions
How do I convert ASF to MP4?
Open this page, add your ASF file, and press convert. The file is decoded and re-encoded by your own browser and saved back to your device. Nothing is uploaded.
Is this ASF to MP4 converter free?
Yes, completely. There is no account, no sign-in, no watermark and no daily limit, because there is no server doing the work. Your own device does it.
Are my files uploaded anywhere?
No. There is no upload endpoint. The conversion runs inside this browser tab, so your file never leaves your device. You can open your browser's network panel and watch: nothing carrying your file is sent.
Is there a file size limit?
No fixed limit. Because the work happens on your machine there is no server quota. The only ceiling is your own device's memory, which for video means very large files may be slow.
Will converting to MP4 lose quality?
MP4 is a lossy format, so some detail is discarded. The quality control on this page decides how much. The default is set high enough that most people cannot see the difference.
Can I convert several ASF files at once?
Yes. Add as many as you like and they are converted one after another, then offered as a single ZIP.