Unity categorizes most saved information into either scene changes or project-wide changes.
Note: If you edit in Prefab Mode, saving through File > Save only saves changes to the open Prefab. Exit the Prefab Mode to save wider changes.
Unity saves some information automatically while you work in the Editor. See Automatic saves for more details.
Scene changes include modifications to GameObjects in the Scene. For example:
Project-wide changes in Unity apply to your entire project rather than a specific scene. For example, if you create a temporary scene to test changes, you can save the project and not the scene.
Project Settings: When you save your project, Unity saves changes to the Project Settings in the
Library folder, in these files:
Build Settings: Unity saves changes to the Build Settings in the
Library folder as
Changed assets: When you save project-wide settings, Unity saves any unsaved assets.
Note: Some asset types have an Apply button in the Inspector. Unity will not save these unless you select Apply.
Dirty assets: Unity saves Dirty assets, which are files on your disk that are modified in the software but not saved yet. You can use custom Editors and scripts to mark an Asset as dirty in one of these ways:
Unity automatically saves the following changes to your disk: