Back up your App Inventor projects by saving them to your computer’s hard drive.
To save a copy of an individual App Inventor project, open the project and select Projects | Export selected project (.aia) to my computer.
Alternatively, with the My Projects list showing all of your App Inventor projects, select Export all projects. App Inventor will create a file named all-projects.zip and download to your computer. The files are compressed and combined into the common .zip file format.
Project files may be read back into App Inventor using the Projects | Import project (.aia) from my computer menu selection.