File Menu: Save Project
Save Project Ctrl + S
Saves the current Audacity Project in uncompressed, lossless quality using the AU container format. An AUP project file is created, along with a folder with the same name as the AUP file that contains the project's audio data. For example, if you save a project as chanson.aup, a folder called chanson_data will contain the audio data files.
If you import uncompressed files such as WAV and AIFF into your project with Import / Export Preferences set to "Read uncompressed audio files directly from the original (faster)", you will create a dependency on those files remaining accessible. In this case, a Dependencies Dialog may appear when saving the project. Follow the instructions in the dialog to either "Copy All Audio..." (so removing all dependencies), or to copy in selected files or none at all. If you choose to not copy in any files, you must not move, rename or delete those files, or the folder they are in. The dialog also lets you choose future behavior when saving a project that depends on imported files.
Save Project As...
Same as "Save Project" above, but allows you to save a copy of an open project to a different name or location. This can be useful if you want to preserve a snapshot of the state of a project at a particular time, then proceed to make further changes to the new renamed project you just saved.
If you "Save Project As..." with a new name, the project window then displays the project name you just "saved as". The project window displaying the project as previously named is closed in its last saved state, but can be reopened as required.
Save Lossless Copy of Project...
Saves a copy of the current Audacity Project in uncompressed, lossless quality, leaving the current project open for you to continue working on it.
If your project has dependent audio files, then using this command will cause a copy of those dependent files to be made in your project's data folder. Then when Audaity is used to reopen the lossless copy project the formerly dependent files will be read and copied into the project. But note that the copies of those audio files will remain in your project's data folder as safety copies.
Save Compressed Copy of Project...
Saves a copy of your project in the compressed Ogg Vorbis format, each track being saved as a separate OGG file. When you quit Audacity you may still be prompted about saving changes. Saving changes would save a separate, standard uncompressed project as above, so if you do not want that you can quit Audacity without saving.
The resulting _data folder for the project is about eight times smaller than that created using either "Save Project" command, so this may be useful for sending projects to others. There will be some resulting loss of quality. Note that the quality loss will be increased each time a compressed project is resaved as a compressed project (for example, if you send a compressed project to someone else, and they then edit it and send it back to you as a compressed project).
Most project data will be retained, including labels, gain and pan settings, track positions on the timeline, track order and metadata. Clips will not be retained - spaces between clips will be converted to silence. Volume envelopes present when saving will be rendered, but the actual envelope points will be lost.
Opening a compressed project will be slower than opening a standard project, because the OGG files in the _data folder will be decompressed into Audacity's AU file format in order to work with the data. The AU files will be in a separate folder inside the _data folder. The OGG files will remain in the _data folder after opening the project, but they can be deleted to save disk space. Similarly when sending a saved compressed project to someone, you can delete any folders containing AU files that are inside the _data folder, because all the necessary data is in the AUP file and the OGG file(s).