What happens when you convert ASF to CAF
- CAF holds sound only, so the picture is discarded and the soundtrack is encoded as Apple Lossless (ALAC) in a Core Audio Format file.
- If the ASF has several audio tracks, the first one is used.
- The CAF holds Apple Lossless, which GarageBand, Logic Pro, QuickTime Player and Apple's own afconvert read. AAC inside a CAF, which some iOS apps use for short sounds, is not written here.
How to convert ASF to CAF online
- Press "Choose ASF files" and select one or more files, or drag them onto the box. You can add files of any size your device can hold in memory.
- Adjust the settings if you need to: the bitrate controls quality and size. The defaults suit most people.
- Press "Convert to CAF". The first audio or video conversion downloads the converter engine, about 32 MB, which your browser then keeps for next time.
- Save each CAF with its download button. Close the tab and every trace of the files is gone from memory.
Why convert ASF to CAF?
ASF files usually come from security cameras, DVRs and old Windows streams. People convert them to CAF because CAF is Apple's own audio format for GarageBand, Logic Pro and sounds inside iPhone and Mac apps, with no limit on file size.
In short, ASF is good at what it was made for, and CAF is the more practical choice when the file has to play on another device or app. ASF does not play in browsers; plays in Windows Media Player, while CAF plays in Safari and Apple apps; not in Chrome or Firefox.
How to convert ASF to CAF on Windows, Mac, iPhone and Android
On Windows
Open this page in Chrome, Edge or Firefox, drag your ASF files in from File Explorer, and press Convert. Each CAF is saved to your Downloads folder. If you prefer a desktop program, VLC can also convert ASF to CAF: choose Media, then Convert / Save.
On a Mac
Safari, Chrome and Firefox all work. Drag the ASF files from Finder onto the drop zone and the CAF files land in Downloads.
On iPhone and iPad
Open the page in Safari and tap Choose ASF files. You can pick from Photos or from the Files app. The converted CAF appears in Files, in the Downloads folder.
On Android
Open the page in Chrome, tap Choose ASF files and pick them from Files or your gallery. The CAF is saved to the Download folder, where any file manager can find it. Keep the screen on while a long video converts, because Android may pause a tab in the background.
Best settings for ASF to CAF
CAF is lossless, so there is no quality setting: every sample of the decoded ASF is kept. What changes is size. CD-quality stereo, 44.1 kHz at 16 bits, takes about 10 MB per minute as uncompressed PCM.
Since the ASF was lossy, the CAF will sound identical to it, not better. Convert to CAF when a program requires it, not to improve quality.
ASF vs CAF: the differences
| ASF | CAF | |
|---|---|---|
| Full name | Advanced Systems Format | Core Audio Format |
| Type | video | audio |
| Created by | Microsoft | Apple |
| First released | 1996 | 2005 |
| Compression | Lossy | Lossy or lossless |
| Usually contains | Windows Media Video and Audio | PCM, AAC, ALAC, Opus and others |
| In a browser | does not play in browsers; plays in Windows Media Player | plays in Safari and Apple apps; not in Chrome or Firefox |
| Common uses | security cameras, DVRs and old Windows streams | GarageBand loops, iOS app sounds and long recordings |
| MIME type | video/x-ms-asf | audio/x-caf |
About ASF and CAF files
What is an ASF file?
ASF is the container behind WMV and WMA. Many CCTV systems and DVRs still export ASF files, which few programs outside Windows will open.
What is a CAF file?
CAF is Apple's container with no practical size limit, while WAV and AIFF stop at 4 GB. It shows up mostly in iOS development and GarageBand projects.
ASF to CAF not working? Common problems
- The conversion is slow. Audio and container changes take seconds, but re-encoding video runs on your own processor. Lower the resolution to 720p, close other tabs, and keep the device plugged in.
- The tab stops or reloads on a very large file. Browsers limit how much memory one tab can use, around 2 GB and less on phones. Split long recordings or convert them on a computer.
- Song titles are missing. Tags such as title and artist are copied when CAF can store them, but cover art is not carried over.
Convert ASF to CAF with ffmpeg
This converter runs ffmpeg inside your browser. If you would rather use the ffmpeg command line on your own computer, this command produces an equivalent CAF with the same kind of settings:
ffmpeg -i input.asf -vn -c:a alac -f caf output.cafReplace input.asf with the name of your file. For a whole folder of ASF files, run the command in a loop, or drop them all on the converter above, which processes them one after another.
ASF to CAF converter FAQ
Will I lose quality converting ASF to CAF?
The sound is re-encoded as Apple Lossless (ALAC) in a Core Audio Format file, which keeps every sample. The picture is not kept.
Why is the CAF a different size from the ASF?
The CAF is much smaller, because the video stream, usually most of the file, is dropped.
Are my ASF files uploaded anywhere?
No. The conversion runs inside this browser tab using ffmpeg compiled to WebAssembly, so your files stay on your device. You can disconnect from the internet after the page and converter engine have loaded and it still works.
Can I convert several ASF files to CAF at once?
Yes. Select or drop as many files as you like; they are converted one after another and each gets its own download button.
How do I open a CAF file?
CAF plays in Safari and Apple apps; not in Chrome or Firefox. CAF is common for GarageBand loops, iOS app sounds and long recordings.
Is this ASF to CAF converter free?
Yes. There is no sign-up, no watermark and no limit on how many files you convert. The site is paid for by advertising, and because conversions run on your device there is no server cost per file.
Can I convert ASF to CAF on my phone?
Yes. The converter works in Safari on iPhone and iPad and in Chrome on Android. Converted files are saved to the Downloads folder.