What quality should I expect from the OPUS output?

Our converter preserves as much fidelity as Opus Audio allows. Where Sun AU Audio carries information that Opus Audio cannot represent, that information is mapped to the closest equivalent (for example, color spaces, codec parameters, or metadata fields). For most everyday uses the result is indistinguishable from the source.

Will my audio metadata (title, artist, album, cover art) be preserved?

Yes, where the target format supports it. Opus Audio can carry standard tag information (ID3, Vorbis comments, or the equivalent depending on the format), and we copy as much metadata as possible from your AU file. Cover art and embedded album artwork are preserved when both formats support it. Highly format-specific metadata that has no equivalent in OPUS is dropped.

What file size should I expect for the OPUS output?

The output size depends on the content and the compression characteristics of Opus Audio. In most cases the OPUS file will be in the same ballpark as your AU input, with differences driven by how each format encodes data. There is no fixed ratio — the converter does not change quality settings unless you ask it to.

When should I convert AU to OPUS instead of staying with AU?

Convert when the application, device, or workflow you are targeting prefers Opus Audio over Sun AU Audio. If your current AU file already opens and behaves correctly everywhere you need it to, there is no benefit to converting — keep the original. The most common reasons to switch are compatibility (a tool only accepts OPUS), distribution (recipients expect OPUS), or feature requirements specific to Opus Audio.

What is the maximum AU file size I can convert?

MegaConvert accepts AU files up to 100 MB on the free service, which is enough for the vast majority of real-world Sun AU Audio files. If you have a larger file (typical for high-resolution video or uncompressed audio), please contact us — we can sometimes accommodate larger uploads for legitimate use cases.

Is my AU file safe and private when I upload it?

Yes. Your AU file is uploaded over HTTPS, processed in an isolated job environment, and deleted from our servers within one hour. We do not read, index, store, or share the contents of your file. No account is required, so the upload is not associated with a personal identity. See our privacy policy for the full details.

Convert AU to OPUS

Free online AU to OPUS converter. No signup required.

Drag & drop your file here

or click to browse

Max file size: 100 MB

Why Convert AU to OPUS?

Understand when and why this conversion makes sense for your workflow.

Converting Sun AU Audio to Opus Audio ensures your audio files work across the widest possible range of devices, players, and streaming platforms. Audio formats differ significantly in their compression algorithms, bitrate support, and metadata handling. Whether you're archiving a music collection, preparing tracks for a podcast, or optimizing audio for a mobile app, selecting the right output format is essential for balancing playback compatibility with sound fidelity.

Sun AU Audio has a known limitation: largely obsolete for general-purpose audio use. In contrast, Opus Audio offers a key advantage: superior audio quality compared to all other lossy codecs at any bitrate. While Sun AU Audio is commonly used for unix and solaris system audio and sound effects, Opus Audio is better suited for voice over ip (voip) and video conferencing applications.

MegaConvert processes your AU file and delivers a properly encoded OPUS output, preserving audio quality within the limits of the target format — free, instant, and private.

AU vs OPUS: Format Comparison

Side-by-side comparison of the source and target formats.

Property	AU (Source)	OPUS (Target)
Extension	.au	.opus
Full Name	Sun AU Audio	Opus Audio
Compression	Varies	Lossy
File Size	Varies	Small
Best For	Unix and Solaris system audio and sound effects	Voice over IP (VoIP) and video conferencing a…
Browser Support	Varies	Wide

How to Convert AU to OPUS

Follow these simple steps to convert your file in seconds.

Upload your AU audio
Drop your .au audio file into the upload zone or browse to select it. Both short voice clips and full-length tracks work — typical Sun AU Audio files (under 100 MB) upload in seconds even on a slow connection. Album art and metadata in the file are read automatically.
Start the OPUS encode
Press the convert button to start. The audio stream is decoded from Sun AU Audio into PCM, then re-encoded as Opus Audio at a quality preset that matches the source bitrate where possible. Sample rate, channel count, and bit depth are preserved unless the target format restricts them.
Wait for the audio to finish encoding
Encoding speed depends on the length of the audio and the codec. Short clips finish in a few seconds; full-length albums can take 30 seconds or so. We do not throttle conversions — the limit is just the encoder's natural speed on the underlying hardware.
Download your .opus file
When the conversion finishes, click the download link to save the new Opus Audio file to your computer. The file is yours — no watermarks, no expiration on the file itself, and no MegaConvert account is required to download it.

Tips for Converting AU to OPUS

Practical advice to get the best results from this conversion.

Why this conversion is worth doing

Sun AU Audio has a known limitation: largely obsolete for general-purpose audio use. Opus Audio addresses this with a key advantage: superior audio quality compared to all other lossy codecs at any bitrate. Converting from AU to OPUS is most worthwhile when this specific trade-off matters for the way you intend to use the file.

Match the format to the actual workflow

Sun AU Audio is most commonly used for unix and solaris system audio and sound effects, while Opus Audio is the standard for voice over ip (voip) and video conferencing applications. If your workflow is closer to the second pattern, converting makes sense. If you are still working in a context where AU is the norm, converting may create unnecessary compatibility friction with collaborators or tools that expect the source format.

Watch for this limitation in the OPUS output

Opus Audio has its own limitation worth understanding before you commit: limited support in older hardware devices and car stereos. After the conversion completes, open the OPUS file and verify that this limitation does not affect your specific use case — for some workflows it is irrelevant; for others it can be a deal-breaker.

Understand lossy vs. lossless before converting

Converting from a lossy format like MP3 to a lossless format like FLAC or WAV does not restore lost audio data — it only changes the container. If you need true lossless quality, always start from an uncompressed or lossless source. Converting lossless to lossy, however, is a valid way to reduce file size for streaming or mobile playback.

Understanding AU and OPUS Formats

Learn about the source and target file formats to understand what happens during conversion.

Source Format

Sun AU Audio

audio/basic

AU is an audio file format introduced by Sun Microsystems and commonly associated with Unix and NeXT systems. It supports various encodings including uncompressed PCM, mu-law, and A-law compression, with a simple header structure. AU was one of the earliest audio formats supported on the web and remains used in Unix-based audio programming.

Advantages

Simple, well-documented format with a minimal header
Native support in Unix, Solaris, and Java audio APIs
Supports multiple encoding types including mu-law for telephony

Limitations

Largely obsolete for general-purpose audio use
Limited metadata support and no modern compression options
Poor support in consumer audio software and devices

Common Uses

Unix and Solaris system audio and sound effects
Java application audio playback (javax.sound)
Legacy telephony and voice processing systems

Target Format

Opus Audio

audio/opus

Opus is a highly versatile, open-source lossy audio codec standardized by the IETF, excelling at both voice and music encoding. It dynamically adapts between low-latency speech coding and high-quality music encoding within a single stream, and consistently outperforms MP3, AAC, and Vorbis in quality comparisons. Opus supports bitrates from 6 kbps to 510 kbps and is designed for real-time interactive audio.

Advantages

Superior audio quality compared to all other lossy codecs at any bitrate
Extremely low latency (as low as 5 ms) ideal for real-time communication
Completely open-source, royalty-free, and standardized by the IETF

Limitations

Limited support in older hardware devices and car stereos
Relatively newer format with smaller existing content libraries
Not yet widely adopted for music distribution despite technical superiority

Common Uses

Voice over IP (VoIP) and video conferencing applications
WebRTC real-time audio in web browsers
Streaming audio where bandwidth efficiency is critical

Frequently Asked Questions

Common questions about converting AU to OPUS.

Related Conversions

Explore other conversions related to AU and OPUS.

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AU to MP3 AU to WAV AU to FLAC AU to AAC AU to OGG AU to WMA AU to M4A AU to AIFF AU to AMR AU to AC3

Other conversions to OPUS

MP3 to OPUS WAV to OPUS FLAC to OPUS AAC to OPUS OGG to OPUS WMA to OPUS M4A to OPUS AIFF to OPUS AMR to OPUS AC3 to OPUS

Convert AU to OPUS

Why Convert AU to OPUS?

AU vs OPUS: Format Comparison

How to Convert AU to OPUS

Upload your AU audio

Start the OPUS encode

Wait for the audio to finish encoding

Download your .opus file

Tips for Converting AU to OPUS

Why this conversion is worth doing

Match the format to the actual workflow

Watch for this limitation in the OPUS output

Understand lossy vs. lossless before converting

Understanding AU and OPUS Formats

Sun AU Audio

Advantages

Limitations

Common Uses

Opus Audio

Advantages

Limitations

Common Uses

Frequently Asked Questions

What quality should I expect from the OPUS output?

Will my audio metadata (title, artist, album, cover art) be preserved?

What file size should I expect for the OPUS output?

When should I convert AU to OPUS instead of staying with AU?

What is the maximum AU file size I can convert?

Is my AU file safe and private when I upload it?

Related Conversions

Other conversions from AU

Other conversions to OPUS