AU to AIFF Converter

AU to AIFF Converter

Two big-endian survivors of late-1980s workstation computing, converted one into the other. Sun and NeXT's .au (also seen as .snd) was the Unix world's audio format, and Apple's AIFF became the Mac and pro-audio standard — both store audio most-significant-byte first, both wrap it in a compact header, and neither is what modern software reaches for by default. The reason to make this trip is that Logic Pro, GarageBand, QuickTime and Pro Tools open AIFF natively while treating .au as an oddity. What you get out, though, is decided by what your AU holds: most legacy .au files are 8-bit telephony audio, and no target format can improve that.

AU Format at a Glance

AIFF Format at a Glance

How to Convert AU to AIFF

1. Upload Your AU File: Drag and drop onto the page or click "+ Add Files" to select .au or .snd files. Batch conversion is supported, so an entire archive folder can go through in one pass with shared settings.
2. Choose the Audio Codec: PCM 16-bit Big Endian is the default and the encoding Apple's applications expect from an AIFF. PCM 16-bit Little Endian, PCM µ-law and PCM A-law are also offered — the µ-law and A-law options keep telephony companding intact instead of expanding it to linear PCM.
3. Set Audio Sample Rate, Audio Channel, or Trim (Optional): Leave Audio Sample Rate and Audio Channel on "ORIGINAL" for a faithful copy — most legacy .au files are 8000 Hz mono, and resampling upward only adds bytes. Trim starts on "Unchanged" and takes a start time plus a duration when you want one sample out of a longer capture.
4. Convert and Download: Click Convert and save the AIFF. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically a few hours later. No sign-up, no watermark.

Frequently Asked Questions

Is converting AU to AIFF lossless?

It depends on what the AU held, and it is worth being precise about the mechanism: our server decodes the source and re-encodes it rather than copying the compressed bytes across. When the AU already contains 16-bit linear PCM and you keep the default PCM 16-bit Big Endian codec at the source's own sample rate, that re-encode involves no lossy stage at all, so the sample values that come out are the same ones that went in. When the AU holds 8-bit µ-law, decoding it to 16-bit linear PCM is mathematically faithful to what µ-law stored — but µ-law had already discarded dynamic range at the moment of recording, and nothing brings that back.

Why is my AIFF so much bigger than the AU?

Because your AU was almost certainly µ-law. G.711 µ-law packs audio at roughly 8 KB per second — 8 bits per sample at 8000 Hz, mono. Expanding that to 16-bit linear PCM for a standard AIFF doubles the bytes per sample immediately, and if you also raise the sample rate the file grows in proportion again. Those extra bytes are a wider container for the same information, not new detail. If you want a small file for listening or sharing rather than an uncompressed master, AU to MP3 is the sensible target.

Will the AIFF sound better than the original AU?

No. Conversion never adds information the source never captured. An 8000 Hz recording is band-limited to roughly 4 kHz of usable audio — the Nyquist limit of that sample rate — so even a large 16-bit AIFF stays firmly at telephone bandwidth. The honest reason to make an AIFF is that Logic, GarageBand, QuickTime and Pro Tools open it without complaint, and that an uncompressed PCM file is a comfortable thing to edit against. Fidelity is fixed at record time.

Which Audio Codec should I choose?

Take the default, PCM 16-bit Big Endian, unless you have a specific reason not to. It is what an AIFF conventionally contains and what Apple's audio applications expect, and it gives you plain uncompressed PCM to edit. Choose PCM µ-law or PCM A-law only when you are making an archival copy of telephony audio and want the original companding preserved byte-for-byte rather than expanded. PCM 16-bit Little Endian exists for tools that specifically want little-endian samples, which is unusual inside an AIFF.

What is AIFF-C, and will my application open it?

AIFF-C (also written AIFC) is the extended version of AIFF that can carry companded and compressed payloads rather than plain PCM. Selecting the µ-law, A-law or little-endian codec here produces that variant, since a standard AIFF is defined around big-endian linear PCM. Modern DAWs, VLC and Audacity read AIFF-C without any fuss, but some older or simpler applications only expect classic AIFF. If a program refuses your file, re-run the conversion on the default PCM 16-bit Big Endian setting and it will accept it.

Why is AIFF big-endian when WAV is little-endian?

History, not merit. AIFF was designed by Apple in 1988 on top of Electronic Arts' IFF-85 chunk format, in the era of big-endian Motorola 68000 processors, so it stores the most significant byte first. Microsoft's WAV borrowed the same chunk idea via RIFF but targeted little-endian x86 hardware. Sun's AU is big-endian for the same generational reason as AIFF, which is a small piece of luck here: the source and the destination agree on byte order, so no sample reordering is involved in the default path. Audibly, endianness makes no difference whatsoever.

Does any metadata survive from the AU?

There is essentially nothing to carry over. The Sun AU header provides only an optional annotation string, and in practice it is usually empty — there are no title, artist, album or track-number fields to begin with. So an empty AIFF metadata panel is not a bug in the conversion; the source genuinely had no tags. Add them afterwards in a tag editor, in Logic or GarageBand, or in whatever library application will hold the files.

Should I convert to AIFF, WAV, or FLAC?

Pick AIFF for Mac-native and pro-audio work, where it is the expected uncompressed format. Pick AU to WAV for cross-platform editing, or when a Windows-side tool or a telephony workflow specifically wants a RIFF file. Pick AU to FLAC when you are archiving a lot of these at once — it stores the same audio losslessly at a fraction of the size, carries proper metadata, and keeps an MD5 checksum so you can prove a decade later that the file is intact. A reasonable pattern is to keep the original .au, make an AIFF or WAV to edit against, and export a small MP3 for sharing.

My file won't convert, or comes out silent — what went wrong?

Check the first four bytes. A genuine Sun/NeXT AU starts with 2E 73 6E 64; anything else is not a standard AU, no matter what the extension says. Two culprits are common in 1990s archives: files corrupted by FTP transfers made in ASCII mode, and headerless raw PCM dumps that were simply given an .au name. The other trap is the extension itself — Sun/NeXT .snd is the same container as .au and converts fine, but classic Mac OS System 7 also used .snd for an entirely unrelated resource-fork sound format, and those pre-OS-X files need a Mac-specific extractor first.

How long are my files kept on your servers?

Your file travels over an encrypted connection, is processed on our servers, and is deleted automatically a few hours after conversion. Nothing is shared or made public, there is no account to create, and no watermark is applied to the output.