Provides well-defined guarantees for fitness, accuracy, and consistency for any of various kinds of user input into an application or automated system. Data validation checks that data are valid, sensible, reasonable, clean, usable, and secure before they are processed. Failures or omissions in data validation can lead to data corruption, security vulnerability. Improperly validated data can cause computer code processing the data to crash, generate error messages, behave in an unanticipated manner, or generate incorrect results that may be difficult or impossible to detect.