AU to M4R Converter

How to Convert AU to M4R Online

1. Upload Your AU File: Drag and drop the .au file onto the page or click "+ Add Files". Classic 8 kHz µ-law clips, A-law files and linear-PCM AU exports from Audacity or SoX all decode, and you can queue several at once.
2. Trim It to Ringtone Length: Most vintage AU sounds are already only a few seconds long. For longer files, open Trim and set a Start time and a Duration of 30 seconds or less, in seconds or HH:MM:SS.sss; the note under Duration repeats Apple's 30-second guidance for iPhone ringtones.
3. Match the Bitrate to the Payload: Under File Compression, choose Constant Bitrate (8 to 384 kbps), one of five Variable Bitrate AAC bands (20k-32k up to 96k-112k), Custom Bitrate or Specific file size; Quality Preset is the hands-off option. A µ-law clip needs only 32-64 kbps in Mono, while 16-bit PCM music deserves 160-256 kbps.
4. Convert and Download: Click "Convert" and save the .m4r. Files are uploaded over HTTPS, converted on our servers and deleted automatically after a few hours. No sign-up, no watermark.

AU: The Unix and Early-Java Sound Format

The AU format (.au, also .snd) comes from Sun Microsystems and NeXT in the late 1980s. A file begins with the four bytes .snd, followed by a short big-endian header that gives the encoding, sample rate and channel count. Its classic form is 8-bit G.711 µ-law at 8,000 samples per second in mono, the same audio a digital telephone line carries, and that combination is what the audio/basic media type describes.

AU was everywhere in the early networked-computer era:

• Unix workstations. Sun and NeXT machines played .au files for system sounds and demos, and Unix tools like SoX still read and write them.
• Early Java. In Java 1.0 and 1.1, applets could only play AU audio, so the beeps, jingles and voices of countless 1990s web games and demo applets are 8 kHz µ-law .au files.
• The early web. Before MP3 took over, .au was one of the formats web pages linked for short sound clips.
• Audio tools and datasets. Audacity and SoX can export AU, and some research audio collections still ship in it.

A retro Unix "boing" or an old applet's victory jingle makes a wonderfully specific text tone. The iPhone, however, will not use an .au file directly: custom ringtones must be .m4r, which is AAC (AAC-LC) audio in an MPEG-4 container, the same container and codec as an .m4a, with the extension that tells iOS, Finder and iTunes the file is a tone. This page decodes the AU and encodes AAC in one step.

Set expectations by encoding. A µ-law or A-law AU at 8 kHz will sound like a phone call as a ringtone, because that is all the file ever held; a linear-PCM AU at 44.1 kHz becomes a full-quality tone. For a regular audio file instead of a tone, use AU to M4A.

AU vs M4R: Format Comparison

Settings by AU Encoding

Sizes are bitrate × seconds ÷ 8, so 48 kbps for 30 seconds is 180 KB. A classic µ-law AU is itself a 64 kbps stream, so encoding it at 64 kbps AAC or higher saves no space at all; 32-48 kbps AAC carries its narrow band comfortably. Since most retro clips are two or three seconds long, the finished tone is usually only 10-20 KB.

Setting the Ringtone on Your iPhone

To get the .m4r onto the phone, the usual routes are: connect the iPhone to a Mac and drag the file onto the iPhone in the Finder sidebar (macOS Catalina or later), or use iTunes on Windows. On the phone itself, save the file to Files, import it into GarageBand and use Share > Ringtone, which Apple documents in Create a custom ringtone on your iPhone. The tone then appears in Settings > Sounds & Haptics > Ringtone (Apple iPhone User Guide); for a single contact, open the contact, tap Edit, then Ringtone or Text Tone.

Frequently Asked Questions

Why does my AU ringtone sound like a telephone?

Because most AU files are 8-bit µ-law at 8 kHz, which was designed for telephone audio and keeps frequencies only up to about 4 kHz. AAC copies that faithfully but cannot add the missing treble. A linear-PCM AU, by contrast, converts into a full-quality tone.

How do I tell which encoding my AU uses?

Run ffprobe file.au and read the codec: pcm_mulaw or pcm_alaw mean 8-bit companded telephone audio, while pcm_s16be and other PCM names mean linear PCM. VLC's codec information window shows the same thing. An 8000 Hz, one-channel file is the classic Sun-era signature.

Will a short two-second sound work as a ringtone?

Yes. A short tone repeats while the phone rings, and it works especially well as a text tone. Apple's GarageBand guide notes that an exported ringtone can be used as a Standard Ringtone or a Standard Text Tone, and custom tones you add appear in both lists.

How long can an iPhone ringtone be?

Apple says ringtones can be up to 30 seconds long, and GarageBand shortens longer ringtones automatically when exporting. The GarageBand for iPhone User Guide gives 30 seconds as the maximum exported length, so keep Duration at 30 seconds or less.

Should I change the sample rate from 8 kHz?

It is not needed. Leaving Audio Sample Rate on Original keeps the AU's rate; choosing 44100 Hz gives a more conventional file but adds no detail, because µ-law audio stops at about 4 kHz.

Is M4R the same as M4A?

The audio inside is: AAC in an MPEG-4 container. We write M4R with the same MPEG-4 muxer as M4A, and ffprobe reports AAC LC in an MP4 file with major brand M4A . Only the extension differs, and it is what makes iOS list the file as a tone. Other formats are covered on the M4R converter page.

Can I convert the M4R back to AU?

Yes, with M4R to AU. The AAC step stays baked in, so keep your original AU. Android users do not need M4R at all, because Android ringtones are usually MP3 or OGG; AU to MP3 suits them better.

What happens to my files?

They are uploaded over an encrypted (TLS) connection, converted on our servers and deleted automatically a few hours after processing. They are never shared or made public, and no account is required.