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Basics
IntelliJ IDEA allows you to work with several projects simultaneously, each one in a separate window. The projects are independent, and cannot share information, except for the Clipboard operations. All the projects run in the same instance of IntelliJ IDEA and use the same memory space.
This behavior is controlled by the options in the section Project opening in the System Settings page of the Settings dialog.
Opening project in a new window
- Open a project, while another one is already open.
- Depending on the selected behavior:
- If the option Open project in a new window is selected, IntelliJ IDEA will silently open new project in a new window.
- If the option Confirm window to open project in is selected, IntelliJ IDEA
will prompt you to specify whether you want to open project in a new window, or close the current
project and reuse the existing window.

Click the New Window button to leave the current project in its window and open the new one in a separate window.
Click This Window button to close the current project and opening the new one in the same window.
IntelliJ IDEA suggests to memorize your choice by selecting the checkbox Remember, don't ask again.