Video format
The ASF format
ASF is Microsoft’s streaming container, found on old CCTV recorders and Windows Media streams. ASF is Microsoft’s 1998 streaming container, the wrapper underneath WMV and WMA files.
When to use ASF
You don’t choose ASF today; you convert it from CCTV systems and old streams.
It is best for old Windows Media streams and security camera exports, and it opens on Windows Media Player and VLC.
How to open it: VLC and Windows Media Player open ASF files.
| Full name | Advanced Systems Format |
|---|---|
| Extensions | .asf |
| MIME type | video/x-ms-asf |
| Introduced | 1998 |
| Compression | Lossy |
| Usually contains | Windows Media or MPEG-4 video with WMA audio |
| Support | Legacy format |
| Typical size | Similar to WMV |
Good at
- Built for streaming over early networks
Not so good at
- Unsupported on Apple devices, phones and the web
The common mistake
CCTV systems often export ASF with timestamps that confuse players, so a recording seems to jump; re-encoding fixes the timing.
Questions
What is an ASF file?
ASF (Advanced Systems Format) is Microsoft’s streaming container, found on old CCTV recorders and Windows Media streams. ASF is Microsoft’s 1998 streaming container, the wrapper underneath WMV and WMA files.
How do I open an ASF file?
VLC and Windows Media Player open ASF files.
How do I convert ASF to another format?
Pick the target on this page, or open the Video Converter, drop the ASF file and choose a format. It converts in your browser, so nothing is uploaded.