- Open an existing project.
- If the project has been created with an older version of IntelliJ IDEA,
you will be prompted to convert the project immediately, or do it later.
- Select the desired option and click Finish.
When you open a project created in one of the previous versions of IntelliJ IDEA, it is converted to the new format. This action is irreversible. After conversion, the older version of IntelliJ IDEA will not be able to read this project any more. However, IntelliJ IDEA creates backup copies of the project files in the special folders projectFilesBackup<n>.
If a project is not converted to the new format, it can still be used, but some of the IntelliJ IDEA features become unavailable. However, you can convert the project later.