Audacity Projects

Audacity project files store information about the entirety of the project - the number of tracks and their time positions, details of clips within the tracks, amplitude envelope points, labels and gain and pan data.

AUP files and project files

Audacity project files store information about the tracks, labels and other project data. They are stored as multiple files: an AUP master file and numerous small AU audio files in subfolders. To get usable audio files in standard formats like WAV or MP3, you must Export them from the project because you can't use AUP for this. Audacity may increase processing speed, and save some space, by referencing external audio files (see Dependencies) rather than making a copy . Note carefully that your project will no longer work if you rename, move, delete or overwrite the original audio file(s) on which it depends! In addition, "summary information" is stored which enables the display to be redrawn rapidly.

Audacity projects contain audio clips arranged onto tracks. The project's structure is:

1. A top level master project file called <my_project_name>.aup
2. A folder at the same filing level called <my_project_name>_data
3. Within the data folder, a sub-folder structure with lots of little .au files which are segments of the recording
4. Also within the folder some housekeeping files which manage the graphical waveform display and carry the links to any external dependent audio files in use by the project

The master project file describes how Audacity links these smaller files together to make up the clips and tracks in the project. The .aup file is in XML format and can be opened in a text editor. The .au files are a lossless, uncompressed format using 4 byte floating point numbers. Their default size is 1 MB or less. This Audacity Project Format is designed to make editing audio faster in Audacity. By updating individual .aup files, which are much smaller than the _data folder, Audacity can move audio around in the project without copying large quantities of data from one place to another.

Note that the format is not compatible with any other audio program. When you Save an Audacity project, you save in the Audacity Project Format, i.e. as an AUP file. An AUP file cannot be played using an MP3 player.

The four rules for keeping your Audacity Project happy:

1. If you import an audio file with the "Read uncompressed file directly from the original (faster)" option checked in Import / Export Preferences (and note this is the Audacity default setting), never move, rename or delete that file, unless you first copy it into the Audacity project. See File > Check Dependencies for more information.
2. Never move, delete or rename any of the files or folders inside the _data folder,
3. Never rename the .aup file or the _data folder.
If you want to rename your project (for example, to save a snapshot at a particular point), use the File > Save Project As... command.
4. Always keep the .aup file and the _data folder together in the same directory (folder).

Opening an Audacity project

When you re-open a project with Audacity you should always Open the <my_project_name>.aup top level file from the File Menu. You should not attempt to open, import or manipulate any individual .au files.

If you have audio which you want to use in Audacity but which wasn't recorded in Audacity, you will need to Import the audio, also from the File Menu.

Dependencies

Depending on your Import/Export Preferences settings, when you open or import an uncompressed audio file such as WAV or AIFF, Audacity saves time by not making a copy of the file (and note carefully that this is the default setting for Audacity's Preferences), instead it refers externally to the original file as you manipulate it within your project (while not ever making any changes to that file unless you tell it to). You must be careful not to modify such audio files with another program while you have them open in Audacity.

When you save a project, providing that you have not changed Audacity's default setting in Projects Preferences settings, Audacity will tell you about these dependencies and give you the option of copying all of the audio data into your project making it safe to delete, move or modify the original audio files if you choose. You can modify the Projects Preferences settings so that Audacity will not ask you but will always either never copy the dependent audio files, or always copy them into the project on exit from Audacity.

At any time you can click on File > Check Dependencies... to see if your project depends on any external files.

Exporting Audio

To use the audio outside Audacity, you need to Export the audio into another format, as described on the File Menu. The format you choose will depend on how you plan to use the audio. For an MP3 player you will want MP3 format, for burning to a CD you will want WAV format.

As noted above .AUP files cannot be used in any other audio program or MP3 player, only in Audacity.

Bill: I realize this may be a low priority, but I and a few others (based on posts on the forum) would love to see a specification of the Audacity XML.

Gale added a note: The summary files have the same format as the audio files, but there are fewer of them. Gale: Importing the same WAV aliased in one project and not so in another produces the same number of .auf files in the aliased project as .au files in the other project (at default blocksize)

• Peter: Gale I'm not sure I really understand this comment - or if we need to retain it on this page?