ASF file format (.asf)
Advanced Systems Format, the Windows Media container.
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What is an ASF file?
In short: An ASF file (.asf) is a video file in the ASF format. ASF is the container; WMV and WMA are what usually sit inside it. It can be converted to MP4, MOV or GIF for free in a web browser with iHateFiles, without uploading it.
Microsoft's Advanced Systems Format, introduced in 1999 as the container beneath WMV and WMA.
ASF is the container; WMV and WMA are what usually sit inside it. It was designed for streaming over the networks of the late nineties, with the ability to start playing partway through a file.
What ASF is good at
- Designed for streaming from the beginning
- Carries video, audio and script commands together
- Native on Windows
Where ASF falls short
- Windows-centric and largely abandoned elsewhere
- Not supported by browsers
- DRM was built into the design
When to use ASF
Convert ASF to MP4.
How to open a ASF file
Windows Media Player and VLC.
| Windows | Windows Media Player, since ASF is the container WMV lives in. |
|---|---|
| macOS | VLC. |
| Linux | VLC or mpv. |
| Phone | VLC. |
| In a browser | No browser plays ASF. |
The thing that usually goes wrong
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.
Questions
What is a ASF file?
Advanced Systems Format, the Windows Media container. Files use the .asf extension.
How do I open a ASF file?
ASF is not widely supported any more. The reliable route is to convert it to a current format, which this page can do in your browser without uploading it.
Can I convert ASF for free?
Yes. Every conversion here is free and unlimited, because your own device does the work rather than a server we have to pay for.
Is ASF lossless?
That depends on the codec inside the container rather than the container itself. Everything written here is re-encoded, so expect one generation of loss.