How do I convert an AU file to MP4 using LetsConvert?

Click Upload and choose your .au or .snd file. Then select the desired audio codec—PCM for lossless output or AAC for smaller file size. Adjust bitrate and sample rate if you like, then press Convert. When the status bar completes, your MP4 is ready to download. There is no need to install anything; everything happens in your browser.

Why should I convert AU to MP4 instead of keeping the AU format?

AU is a legacy Sun/NeXT format chiefly used in Unix and Java development. MP4 is the universal container for online video and audio—supported natively by Windows, macOS, iOS, Android, and all modern web browsers. Converting to MP4 with AAC lets you cut file size by 70–90% while maintaining reasonable quality, making it easier to email, upload, or stream.

What metadata and audio attributes are preserved when converting AU to MP4?

With PCM output, the decoder reads the AU header's encoding, sample rate, and channels (e.g., 8-bit μ-law at 8 kHz) and expands it to linear PCM within the MP4 file—no resampling or quality loss. With AAC output, the encoder re-samples to a chosen rate, discards imperceptible frequencies, and stores compressed audio; you can set a constant bitrate between 64 and 320 kbps. Metadata like the AU comment field is mapped to MP4's ©nam/©cmt atoms.

Is AU-TO-MP4 free to use?

Yes, AU-TO-MP4 on LetsConvert is 100% free with no registration or hidden fees required.

Are my uploaded files safe and secure?

Yes! File privacy and security are guaranteed. Basic conversions run locally in your browser. Files sent for server processing are automatically deleted within 1 hour.

Does this converter work on mobile phones and tablets?

Yes! AU-TO-MP4 works seamlessly across iPhone, Android, iPad, Mac, Windows, and Linux browsers without installing any app.

Is there any software installation required?

No software or browser extension installation is needed. All conversions are performed directly online.

AU➔MP4· 100% Free & Full HD

AU-TO-MP4

Convert Sun AU audio to MP4 (AAC) for universal media player and browser support. Choose lossless PCM or AAC compression with custom bitrate.

★★★★★

4.7 / 5.0(41 user ratings)

Rate this tool:

🎬

Choose Au video file or drag & drop here

Supports up to 50MB · Hardware accelerated transcode

Browse Video

Or import from:

📢

Share AU-TO-MP4Recommend this free tool to your friends & colleagues

📁

AU

AU File Format

Source Format

AU is a standardized digital file format supported by LetsConvert. Convert AU files securely, privately, and instantly online with zero software installation, bank-grade encryption, and automatic 60-minute file purging.

Category: Data & Media File

MIME Type: application/au

Developer: Standard Organization

Best For: Converting and managing AU files across devices and applications.

✨

MP4

MPEG-4 Part 14 Video Container

Target Output

MP4 is the undisputed global standard digital video format. Supported across every computer, smartphone, smart TV, browser, and social platform, it encapsulates high-efficiency H.264/H.265 video and AAC audio with unmatched playback reliability.

Category: Digital Video

MIME Type: video/mp4

Developer: Moving Picture Experts Group (MPEG)

Best For: Social media video, YouTube uploads, mobile video recording, web video streaming, and video archiving.

💡 Technical Guide & Conversion Insights

Why Convert AU to MP4?

Converting from AU (AU File Format) to MP4 (MPEG-4 Part 14 Video Container) is essential when you need enhanced compatibility, reduced file size, or specific feature support. While AU is ideal for Converting and managing AU files across devices and applications., MP4 offers superior advantages for Social media video, YouTube uploads, mobile video recording, web video streaming, and video archiving.. Our secure online conversion engine ensures that all your AU file attributes, geometry, quality, and metadata are seamlessly preserved during the transformation into MP4.

● AU Key Advantages:

✓Standard format compatibility
✓Fast online conversion processing
✓Zero software install required

● MP4 Key Advantages:

★100% universal hardware and software playback compatibility
★High compression efficiency with excellent HD/4K fidelity
★Optimal format for YouTube, TikTok, Instagram, and web embedding

AU vs MP4 Comparison Table

Detailed technical differences and capabilities between AU File Format and MPEG-4 Part 14 Video Container.

Feature / Attribute	AU	MP4
Primary Format Name	AU File Format	MPEG-4 Part 14 Video Container
Primary File Category	Data & Media File	Digital Video
Standard MIME Type	application/au	video/mp4
Core Developer / Standard	Standard Organization	Moving Picture Experts Group (MPEG)
Optimal Use Case	Converting and managing AU files across devices and applications.	Social media video, YouTube uploads, mobile video recording, web video streaming, and video archiving.

❓ Common Questions

Frequently Asked Questions (AU to MP4)

Everything you need to know about converting AU to MP4 with LetsConvert.

To convert your AU file to MP4, upload your file by dragging and dropping it into the upload box or selecting it from your device. Adjust any optional quality or dimension settings, then click 'Convert'. Your converted MP4 file will be ready for instant high-speed download within seconds.

🛡️

100% Secure & Automatic File Purging

Your AU files are encrypted with 256-bit SSL and permanently deleted from our servers within 60 minutes.

● Zero File Storage

How to Convert AU-TO-MP4

Select or drop your Au file.

Initiate the MP4 conversion process.

Download your converted MP4 file.

⚡ Related Video Tools

AU-TO-MP4

AU

MP4

Why Convert AU to MP4?

● AU Key Advantages:

● MP4 Key Advantages:

AU vs MP4 Comparison Table

Frequently Asked Questions (AU to MP4)

100% Secure & Automatic File Purging

How to Convert AU-TO-MP4

Related Video Converters (145)

3G2 to MP4

3GA to MP4

3GP to AU

3GP to MP4

3GPP to MP4

AAC to MP4

AIF to MP4

AIFC to MP4

AIFF to MP4

ALAC to MP4

AMR to MP4

APE to MP4

ASF to AU

ASF to MP4

AU to 3GP

AU to ASF

AU to AVI

AU to FLV

AU to GIF

AU to M2TS

AU to MKV

AU to MOV

AU to MPEG

AU to MPG

Explore All VIDEO Pairs & Formats

⚡ Convert from AU to other formats: