AU Converter

How to Convert AU to Any Format

1. Upload Your AU File: Drag and drop your .au (or .snd) file or click "Add Files". Batch is supported — drop in several AU files and each one converts in parallel, then download them together as a ZIP.
2. Pick an Output Format and Quality Preset: Choose the target under Audio File Extension — MP3, WAV, FLAC, AAC, OGG, M4A, Opus, AIFF, WMA, and more. The default Quality Preset is "Very High (Recommended)"; switch to Constant Bitrate for predictable streaming sizes, Custom Bitrate to type an exact kbps value, or Specific file size to cap output at an exact MB target.
3. Adjust Sample Rate, Channels, or Trim (Optional): Under Audio Sample Rate, keep the original (often 8000 Hz for classic AU) or resample up to 48000 Hz; set Audio Channel to Original, Mono, or Stereo; and use Trim to keep only a start point and duration. Advanced users can override the Audio Codec directly.
4. Convert and Download: Click Convert. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared.

Popular AU Conversions

• AU to MP3 — small, universal files that play on every phone, browser, and media app
• AU to WAV — uncompressed PCM for editing in any DAW or Audacity
• AU to FLAC — lossless archival at roughly half the size of WAV
• AU to AAC — efficient playback in the Apple ecosystem and on modern devices
• AU to OGG — royalty-free Vorbis audio for the open web and games
• AU to M4A — AAC-in-MP4 for iTunes, Apple Music, and iOS

Why Convert an AU File?

AU (also written .snd) is the Sun Microsystems audio format — a simple, single-stream container that originated in the late 1980s on NeXT and Sun Unix workstations and was common in early Solaris, Java applets, and the first generation of audio on the web. In its classic form it was headerless 8-bit G.711 μ-law data sampled at 8000 Hz; the headered version adds six big-endian 32-bit words and supports linear PCM and other encodings. It is a legacy format today — you mostly meet .au files when opening old archives, Unix system sounds, Java teaching material, or preserved web pages.

The reasons to convert away from AU are almost always about reach and quality:

• Playback anywhere — most phones, browsers, and consumer apps no longer open .au out of the box. MP3, AAC, or M4A play everywhere, so converting is the fastest way to make an old recording usable again.
• Editing — DAWs and editors like Audacity, Reaper, or Logic prefer linear PCM. Converting AU to WAV gives you a clean, uncompressed working file. (Note: Audacity also writes its own internal .au project files, which are unrelated to the Sun format and are not meant to be opened directly.)
• Fixing low-fidelity μ-law audio — classic 8-bit μ-law at 8000 Hz is telephone-grade. Converting does not add detail that was never recorded, but moving to a 16-bit PCM WAV or FLAC stops further degradation and gives editors clean headroom to denoise or normalize.
• Archiving — FLAC stores the decoded audio losslessly at roughly half the size of WAV, with metadata tags AU never supported, which makes it a better long-term home for a legacy collection.

AU at a Glance

Frequently Asked Questions

What is a .au file and what opens it?

A .au (or .snd) file is Sun Microsystems' audio format — a single-stream container that originated on NeXT and Unix workstations and is now legacy. Desktop players that still open it include VLC, Audacity, Apple QuickTime, and older builds of Windows Media Player, but most browsers and phone apps no longer recognize it. The simplest fix is to convert it to a modern format like MP3 or WAV, which then plays in anything.

Is AU compressed or lossless?

It depends on the encoding inside the file. The classic AU is 8-bit G.711 μ-law — a lightly compressed, telephone-grade format that loses detail. But AU can also hold uncompressed 16-bit (or higher) linear PCM, which is effectively lossless. Converting a μ-law AU to WAV gives you the exact same audio in a PCM wrapper without further loss; converting a PCM AU to FLAC keeps it lossless while shrinking the file.

Will converting AU to MP3 improve the sound quality?

No conversion can add detail that was never captured. A classic 8000 Hz μ-law AU will still sound telephone-grade after conversion — MP3 just makes it playable everywhere. If your AU contains higher-quality PCM, choose a generous MP3 bitrate (256–320 kbps) or convert to a lossless target like WAV or FLAC to avoid stacking a second round of lossy compression on top.

What's the best format to convert an AU file to for everyday playback?

MP3 is the safest universal choice — it plays on every phone, browser, car stereo, and media app, and a 192–320 kbps file is indistinguishable from the source for most listeners. If you live in the Apple ecosystem, AU to M4A (AAC) gives slightly better efficiency at the same bitrate. For editing rather than listening, pick WAV instead.

Does converting AU preserve metadata like title or artist?

The AU format has no native tag fields the way MP3 (ID3) or FLAC (Vorbis comments) do, so there is usually no embedded title or artist to carry over — only the sample rate, channel count, and encoding, which are preserved. If you want tags, convert to MP3, M4A, or FLAC and add them in your player or editor afterward.

How do I convert a whole folder of AU files at once?

Drop all of them onto the converter at once. Batch is supported and each file converts in parallel, so you can queue a legacy archive and download every result together as a single ZIP. In our testing, a folder of short 8000 Hz μ-law AU clips converts almost instantly per file, since μ-law decoding is trivial and the bottleneck is upload time rather than processing.

Is it safe to upload old AU files here?

Yes. Files are uploaded over an encrypted (TLS) connection, processed on our servers, and deleted automatically after a few hours. There is no sign-up, no watermark, and your files are never shared or made public — the only practical limit on a large batch is your upload speed, not your device.