CONVERT
AU → WMA
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Fast, secure AU to WMA conversion. No registration required.
Here is the short version — AU is the Sun/NeXT audio format, a historical PCM container still found in older pipelines. Hence the need for WMA. A AU to WMA transcode is mostly about compatibility, not fidelity. At sensible default bitrates you cannot tell the two apart by ear; what you get is a file that actually opens on the hardware or website you were aiming at. FFmpeg handles the heavy lifting and we stream the result straight back as a download. In practice AU is the Sun/NeXT audio format, a historical PCM container still found in older pipelines. On the other end, WMA is Microsoft's proprietary audio codec, historically tied to Windows Media Player.
Sun AU Audio
Source formatAU is a simple audio format from Sun Microsystems, commonly used on Unix systems.
Windows Media Audio
Target formatWMA is a proprietary Microsoft audio format from the Windows Media framework. Once common in the Windows ecosystem, it has been largely replaced by AAC and MP3 for general use.
Why convert AU to WMA
Moving from AU to WMA usually buys compatibility or a friendlier file size. For spoken-word content the difference is inaudible; for high-resolution music pick the highest bitrate the WMA codec supports to avoid compounding compression.
HOW TO CONVERT
AU → WMA
Provide the audio file
Drag the AU onto the uploader. Files up to 25 MB run on the free tier without registration; paid plans go up to 2 GB.
ffmpeg handles the conversion
Our ffmpeg-based pipeline reads sample rate and channel layout, then writes a matching WMA with ID3 tags intact.
Save the output
Click to download the WMA. Batch uploads are bundled into a ZIP for single-click retrieval.
Common Use Cases
Share across platforms
Send WMA files to anyone without worrying about whether they have the right software for AU.
Embed in documents
Drop WMA output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
WMA often produces smaller files than AU for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
AU vs WMA — Strengths and limitations
What each format does best, and where it falls short.
AU Strengths
- Trivially simple format — 24-byte header, then samples.
- µ-law 8-bit variant fits hours of speech in kilobytes.
- Stable since 1988; every major audio library reads it.
- Streaming-friendly: size field is optional.
Limitations
- Aging — obsolete outside legacy and compatibility scenarios.
- No metadata beyond a single annotation string.
- No native multi-channel surround support.
WMA Strengths
- Good quality at low bitrates (32-64 kbps) — outperformed MP3 in that range.
- Native playback on every Windows version 2000 through 10.
- Lossless variant available (WMA Lossless) for archiving.
- Supports multichannel 5.1 surround audio.
Limitations
- Proprietary — poor support outside Windows and Windows Media Player.
- DRM variants made files brittle — many purchased tracks became unplayable when stores shut down.
- Ecosystem abandoned — no modern editors, hardware decoders, or streaming services use WMA.
AU vs WMA — Technical specifications
Side-by-side comparison of the technical details.
AU
- MIME types
- audio/basic, audio/au, audio/x-au
- Extensions
- .au, .snd
- Header
- 24 bytes (magic, offset, size, encoding, rate, channels, info)
- Codecs
- PCM 8/16/24/32-bit, µ-law, A-law, IEEE float
- Byte order
- Big-endian
WMA
- MIME type
- audio/x-ms-wma
- Extension
- .wma
- Container
- ASF (Advanced Systems Format)
- Variants
- WMA Standard, WMA Pro, WMA Lossless, WMA Voice
- Max bitrate
- 768 kbps (WMA Pro)
| Specification | AU | WMA |
|---|---|---|
| MIME types | audio/basic, audio/au, audio/x-au | — |
| Extensions | .au, .snd | — |
| Header | 24 bytes (magic, offset, size, encoding, rate, channels, info) | — |
| Codecs | PCM 8/16/24/32-bit, µ-law, A-law, IEEE float | — |
| Byte order | Big-endian | — |
| MIME type | — | audio/x-ms-wma |
| Extension | — | .wma |
| Container | — | ASF (Advanced Systems Format) |
| Variants | — | WMA Standard, WMA Pro, WMA Lossless, WMA Voice |
| Max bitrate | — | 768 kbps (WMA Pro) |
AU vs WMA — Typical file sizes
Approximate file sizes for common scenarios.
AU
- 10-second clip (8-bit µ-law, 8 kHz) 80 KB
- 10-second clip (16-bit PCM, 44.1 kHz stereo) ~1.7 MB
WMA
- 3-min song (128 kbps) 3 MB
- 3-min song (Lossless) 25-35 MB
- 1-hour talk (64 kbps) 28 MB
Quality & Compatibility
Sample rate, channel layout and bit depth are preserved by default: a 44.1 kHz stereo AU becomes a 44.1 kHz stereo WMA. Metadata — title, artist, album, cover art — travels where both formats support it. Protected DRM content cannot be converted legally and is rejected.
Tips for Best Results
- Check the podcast host specification before choosing bitrate — some mandate CBR 64 kbps, others accept VBR up to 192 kbps.
- Preserve ID3 tags by editing them before conversion; Mp3tag and MusicBrainz Picard handle round-tripping cleanly.
- If the AU is 24-bit studio audio, the WMA at 16-bit is sufficient for listening; higher is wasted on consumer playback gear.
Frequently Asked Questions
Lossy-to-lossy conversions (most combinations) re-compress the audio, which technically introduces some loss. At a 192 kbps or higher target it is inaudible on normal equipment. Lossy-to-lossless conversions freeze the existing quality but cannot improve it; lossless-to-lossy transcodes are only as good as the target bitrate you choose.
For voice content (podcasts, audiobooks, lectures) 128 kbps is indistinguishable from higher bitrates. For music, 192-256 kbps covers most listening; 320 kbps is the ceiling for WMA and the right choice for audio you plan to edit further. Above that, prefer a lossless target instead.
Yes. Title, artist, album, year and cover art travel from the AU container to the WMA container automatically where both formats support them. If a tag field has no WMA equivalent, it is dropped silently. Use any tag editor (Mp3tag, MusicBrainz Picard) to fine-tune afterwards.
Related comparisons
See these formats side by side to understand which fits your use case best.
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