App icon size
96 x 96 px (recommended)
Up to 10 (recommended)*
The precise limits depend on several different factors such as the size of your app, the storage taken up by sounds and images, the speed of your network connection, and the configuration of your Web browser. But as you keep adding screens, you’ll run across one or more of these factors, and the consequences could be very unpleasant. This could include the Blocks editor running more and more slowly, and the inability of Thunkable to build your project. In extreme cases, you could exceed the capacity of App Inventor to save or load your project: you would be stuck with no way to view or even fix your project and you’d have to ask for help on the forum, and even the people there might be unable to help.
If you’re building an app with more than 10 screens, save your project (aia file) to your local computer -- not just the Thunkable server -- each time you make a significant change. It’s a good idea to save the versions of the project under different names, like MyAppV1, MyAppV2, and so on. That way, if you do run into a problem, you have a history of versions to examine. Be especially careful if you add a lot of screens to a project at once. That’s a likely time to run into problems.
Making a series of backups like this is a good idea, not only in the case of multiple screens, but any time you are working on large and complex projects. There is always a risk of losing your work, and it’s worth the effort to make backups as a precaution.