CONVERT FLAC → AU (FLAC to AU)
Fast, secure FLAC to AU conversion. No registration required.
📈 Target Minimum File Size (Guaranteed ≥ KB)
Lossless JPEG Q100 + standard COM segment padding for government & exam portals
Tap to choose your file Drop files here or click to browse
Automatic format identification and lossless transcoding across 201+ formats.
Convert to:
Detecting available formats...
Target Max File Size:
Uploading...
Processing your file...
READY!
Download File
Your file is converted & verified! Unlock instant download:
One-time secure payment via Stripe (Apple Pay, Google Pay, Card). Zero recurring subscription.
🛡️ Verification Audit
- ✓
- ✓ sRGB Color Fidelity
- ✓
Continue with this converted file (0s zero re-upload):
Batch Conversion Ready!
Your file is converted & verified! Unlock instant download:
One-time secure payment via Stripe (Apple Pay, Google Pay, Card). Zero recurring subscription.
Need to convert larger files or bigger batches right now?
Unlock up to 1 GB & priority cloud queue with 1-click Stripe checkout (Apple Pay, Google Pay, Card):
HOW TO CONVERT FLAC → AU
Upload the FLAC
Drop or select your FLAC file. The upload is encrypted and the file is queued for conversion.
Transcode via FFmpeg
FFmpeg decodes the FLAC stream to PCM internally, then re-encodes as AU at the bitrate you select.
Download the AU
The AU is delivered as a direct download; metadata and cover art transfer automatically where possible.
FLAC is the Free Lossless Audio Codec, offering 40–60% compression with zero quality loss. That is why users land on this page looking for a AU copy. Need a AU version of a FLAC recording for a podcast host, audio book platform or DAW that refuses the original container? Drop the file above and our encoder produces a clean AU you can drag straight into the destination tool. Metadata such as title, artist and cover art travels with the audio. Keep in mind FLAC is the Free Lossless Audio Codec, offering 40–60% compression with zero quality loss. And remember that AU is the Sun/NeXT audio format, a historical PCM container still found in older pipelines.
Why convert FLAC to AU
FLAC Audio is great in its own niche, but Sun AU Audio is either more universally playable or better suited to the device you are targeting. Converting lets you ship the audio without asking listeners to install a codec. The loss in quality between the two is negligible at sensible bitrates.
FLAC vs AU — Technical specifications
Side-by-side comparison of the technical details.
FLAC
- MIME type
- audio/flac
- Extension
- .flac
- Standard
- Open-source reference implementation (Xiph.Org)
- Max bit depth
- 32 bits per sample
- Max sample rate
- 655 350 Hz
- Max channels
- 8
- MIME Type
- audio/flac
- Category
- Audio Files
- Full Name
- FLAC Audio
- Conversion Engine
- FFMPEG
AU
- Extension
- .au
- MIME Type
- audio/basic
- Category
- Audio Files
- Full Name
- Sun AU Audio
- Conversion Engine
- FFMPEG
- 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
| Specification | FLAC | AU |
|---|---|---|
| MIME type | audio/flac | — |
| Extension | .flac | .au |
| Standard | Open-source reference implementation (Xiph.Org) | — |
| Max bit depth | 32 bits per sample | — |
| Max sample rate | 655 350 Hz | — |
| Max channels | 8 | — |
| MIME Type | audio/flac | audio/basic |
| Category | Audio Files | Audio Files |
| Full Name | FLAC Audio | Sun AU Audio |
| Conversion Engine | FFMPEG | FFMPEG |
| 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 |
FLAC vs AU — Strengths and limitations
What each format does best, and where it falls short.
FLAC Strengths
- Lossless — decoded audio is bit-exact identical to the source.
- 40-60% smaller than uncompressed WAV/AIFF.
- Free, patent-free, open-source reference implementation.
- Built-in error detection via MD5 checksums.
- Streaming-friendly — seek tables let you jump to any timestamp instantly.
Limitations
- File sizes still large compared to lossy codecs (5-10× bigger than AAC for same audio).
- Not suitable for low-bandwidth scenarios like streaming on mobile data.
- Older MP3 players and car stereos may not decode FLAC.
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.
Quality & Compatibility
Lossy-to-lossy transcoding (most cross-format audio jobs) loses a tiny amount of quality on each pass — usually inaudible at our default VBR ~190 kbps for music or 96 kbps for speech. Lossy-to-lossless conversions freeze the existing quality but cannot improve it; lossless-to-lossy is only as good as the target bitrate you choose.
Tips for Best Results
- Pick 128 kbps for podcasts and voice, 192–256 kbps for music, 320 kbps only if the audio will be edited further downstream.
- Keep the FLAC master alongside the AU — re-encoding a lossy format twice accumulates audible artefacts.
- For mono voice content, convert to mono AU explicitly to halve file size without any quality loss.
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 AU 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 FLAC container to the AU container automatically where both formats support them. If a tag field has no AU equivalent, it is dropped silently. Use any tag editor (Mp3tag, MusicBrainz Picard) to fine-tune afterwards.
FLAC Audio
Source formatFLAC is an open-source lossless audio codec that compresses audio to roughly 50-60% of its original size without any quality loss. It is the preferred format for audiophiles and music archival.
Sun AU Audio
Target formatAU is a simple audio format from Sun Microsystems, commonly used on Unix systems.
Going the other way? Convert AU back to FLAC with the same engine.
Common Use Cases
Share across platforms
Send AU files to anyone without worrying about whether they have the right software for FLAC.
Embed in documents
Drop AU output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
AU often produces smaller files than FLAC 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.
FLAC vs AU — Typical file sizes
Approximate file sizes for common scenarios.
- 3-min song (CD quality) 20-30 MB
- Full album (10 tracks, CD) 250-400 MB
- 3-min song (hi-res 24-bit/96 kHz) 80-120 MB
- 10-second clip (8-bit µ-law, 8 kHz) 80 KB
- 10-second clip (16-bit PCM, 44.1 kHz stereo) ~1.7 MB
Lossless 24-bit Hi-Res Audio or Full Discographies?
Converting pristine FLAC/ALAC collections while preserving 192kHz master dynamics without exhausting mobile bandwidth? Dedicated multi-threaded workstation converters handle entire folders instantly.
One-time payment with zero recurring commitment: convert files up to 1 GB, OCR, PDF/A, and .ZIP batches for 24 hours.
Full 7 days of unlimited conversions, up to 2 GB per file, 100% ad-free with zero subscription.
High-throughput enterprise pipeline for files up to 2,048 MB, 50-file batches, ISO PDF/A, and priority processing.
Lossless batch chain processing preserving full ID3v2 metadata tags and embedded artwork.
Multi-CPU discography conversion with AccurateRip CRC verification and DSP mastering.
Related comparisons
See these formats side by side to understand which fits your use case best.
Related Guides
Opus Audio Format: The Complete Technical Guide
Complete technical guide to Opus audio: SILK and CELT engines, hybrid mode, bandwidth modes, bitrate reference from 6 to 510 kbps, Ogg Opus container...
Read guide →AAC Audio Format: The Complete Technical Guide
Complete technical guide to AAC: AAC-LC, HE-AAC v1/v2, AAC-ELD profiles, MDCT filter bank, TNS, PNS, joint stereo, bitrate reference, M4A vs ADTS containers...
Read guide →FLAC: The Complete Guide to Free Lossless Audio Codec
Complete technical guide to FLAC: file structure, STREAMINFO MD5, linear predictive coding, Rice entropy coding, compression levels 0–8, ReplayGain, FLAC vs...
Read guide → </> Embed this tool on your website or blog (Free) ▼
Add this converter to your site in 10 seconds
Help your visitors convert files directly from your documentation, CMS, or blog. Copy the lightweight HTML snippet below — zero dependencies, responsive, and 100% free.
Secure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.