Convert AU to VTT

Sonix transcribes your AU file and exports it as WebVTT captions perfect for HTML5 video and web platforms.

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HTML5 ready
5-min turnaround
Web compatible
AU conversion guide

Convert AU to VTT in 6 steps

  1. 1
    Create account~30 sec

    Sign up for a free Sonix trial with 30 free minutes.

  2. 2
    Upload file~1 min

    Upload your AU file from your computer or cloud storage.

    44+ formats supported
  3. 3
    Select language~10 sec

    Select the language spoken in your file.

    54+ languages
  4. 4
    Auto-transcribe~5 min

    Sonix AI transcribes and timestamps your AU audio.

  5. 5
    Edit captions~2 min

    Fine-tune caption timing and text in the editor.

  6. 6
    Export VTT~10 sec

    Download your AU captions as a WebVTT file.

    30+ export formats
The AU file format

Understanding AU files

What is a AU file?

Audacity project audio chunks

Audacity, an open source audio editor, breaks long tracks into small pieces so it can edit them more efficiently. Thus, when you save an Audacity Project File (.AUP), Audacity will automatically create a _data folder that has the same name as the AUP file and breaks the longer audio file into smaller chunks that have the .AU extension. Thus, when Audacity opens up the AUP Project File, it loads the individual AU files in the correct sequence automatically. The user should not move or rename and AU files in the _data folder.

Common uses for AU files

  • Audacity audio editing
  • Audio project files
  • Audacity project folders

Who works with AU files?

Podcast editors and home-studio producers usually run into AU files when recovering audio from legacy Audacity projects, since older versions of the editor stored each track as small AU chunks. Unix system administrators and Java developers may also recognize the format from its origins as the standard sound file on Sun and NeXT workstations.

AU vs WAV: which should you use?

AU and WAV are both simple header-plus-data audio formats: WAV, created by Microsoft and IBM, became the de facto standard for uncompressed audio, while AU originated on Sun and NeXT systems and survives mainly in legacy Unix software and older Audacity project folders. Both can hold uncompressed PCM, but WAV has far broader support in modern editors, players, and web tools. Choose WAV when exporting or sharing audio; AU is typically something a legacy project or system hands to you rather than a format you pick.

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AU conversion FAQ

AU to VTT: frequently asked questions

Can you convert AU to VTT captions?

Yes! Sonix transcribes your AU file with precise timestamps and exports it as WebVTT captions for web video.

What is a VTT file?

WebVTT (Web Video Text Tracks) is the native caption format for HTML5 video. It's supported by all modern browsers and video platforms.

VTT vs SRT - which should I use?

Use VTT for web video (HTML5) and SRT for video editors. VTT supports advanced styling like colors and positioning.

Does VTT support styling?

Yes! VTT supports CSS styling for colors, fonts, positioning, and more. Customize how your captions appear on screen.

Is VTT compatible with browsers?

VTT is supported by Chrome, Firefox, Safari, Edge, and all modern browsers. It's the web standard for video captions.

Can I use VTT with video.js?

Absolutely! VTT works seamlessly with video.js, Plyr, JW Player, and other HTML5 video players.

Why is my Audacity project folder full of small AU files?

Older versions of Audacity split a project's audio into small AU block files inside a _data folder so long tracks could be edited efficiently, and the .aup project file reassembles them in order. Avoid moving or renaming these chunks; open the project and export the audio instead.

How do I play a standalone AU file?

Standalone AU files use the Sun audio format and open in players such as VLC and editors such as Audacity. Converting to WAV or MP3 gives the broadest compatibility with modern software and devices.

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