Help: File size differences when using "Save As" and "Save As Lossless"

  1. Original recording project file (_data): 5.48 GB
  2. Cut a large chunk of silence at the end and Save Project As a different name: 1.85 GB
  3. Opened #1 again, did the same cut, but used Save Lossless Copy of Project: 3.69 GB
  4. Opened #3, Save Project As a different name: 1.85 GB

Can someone explain the descrepancy between 2 and 3? Why does Save Project As have a different file size than Save Lossless Copy of Project when theoretically they should be exactly the same?

From what I understood, the two options are the same and the only difference is whether you continue editing in the original file or the newly saved one. Am I wrong? Does Save As do something different than Save Lossless Copy?

Windows 10
Audacity 2.3.3

Sometimes the sizes will be the same, and sometimes the “Save Lossless Copy” will be bigger.

In an “ordinary” (Save Project As…) project:

  • Silence may be either blocks of silent audio, or they may be “virtual” blocks with no actual audio data.
  • Imported WAV / AIFF / other PCM format files may be copied into the _data folder (default), or may be “linked dependencies” that are external to the project.
  • Duplicated audio clips may share the same audio data.

In a “lossless copy” of the project, all audio, including silence and “dependencies”, are rendered inside the _data folder as 32-bit float WAV files. The “lossless copy” is guaranteed to contain all of the project’s audio data, which makes it safer when storing projects. Even if the project’s “AUP” file gets trashed, the _data folder will still contain 100% of the audio data, as one WAV file per track. Lossless copies are thus well suited for backups, provided that you have sufficient disk space.

Thank you very much! I’ll use Save As Lossless every time from now on since this project is very valuable to me.

In that case it may be worth also making an occasional backup to external media (thumb drive or external hard drive) as an extra safety level.