# Project Validation
One of the key features of appRules is that the system provides several options for validating activities on the designer, functions, expressions, data source metadata and other items used in the development of your projects.
## Design Time Validation
When using appRules Designer, at design time, appRules flags all activity errors on the designer (using a red dot). You can mouse over the error flag to view the error message. As each error is corrected, the error flag is removed.
## Detailed Validation of appRules Projects
At any time, you can perform a detailed validation of your projects.
To perform a detailed project validation, display the Project Validation modal as follows:
Click the Validate button from appRules project toolbar for validation the current project.
The project is validated and the results are displayed as shown below:
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