Data validation is crucial in modern web applications to ensure data quality, accuracy, and security while reducing development time. The article outlines a multi-level approach to data validation in full stack applications using React, covering the frontend, backend, and database levels. On the frontend, validation is implemented to enhance user experience and reduce server load, using built-in HTML attributes, custom JavaScript, or open-source libraries. Backend validation is performed to verify data before saving it to the database, often using frameworks based on the Model-View-Controller architecture, while ensuring endpoint security to prevent bypass attempts. At the database level, validation is achieved through a well-designed schema and constraints like default values, uniqueness, and foreign keys, ensuring data integrity across all layers. This comprehensive validation strategy helps create reliable, user-friendly applications by maintaining clean and consistent data.