# Customizing the initial program state

When OVITO starts, it searches for a file named `defaults.ovito` on your system. If found, this file is used to initialize the session, allowing you to override factory defaults for various settings. This feature saves time by preserving your preferred configuration across sessions.

The `defaults.ovito` file can define:

- The initial viewport layout.

- The projection type and camera orientation for each viewport.

- The render settings.

This mechanism is independent of other application-wide settings, which can be modified in the Application settings dialog and are stored separately in a configuration file.

## File locations

OVITO searches for the `defaults.ovito` file in the following locations:

Windows: | `C:\Users\<USER>\AppData\Roaming\Ovito\Ovito\defaults.ovito`
Linux: | `~/.local/share/Ovito/Ovito/defaults.ovito`
macOS: | `~/Library/Application Support/Ovito/Ovito/defaults.ovito`

To create a `defaults.ovito` file, use File ‣ Save Session State As in OVITO. Ensure the saved session is empty (i.e., contains no datasets and pipelines), as this file serves only as a blank starting template before you import simulation data.