Active Record validations are used to ensure that only valid data is saved to the database by validating the objects before they are saved. Active Record has a validation system allowing developers to specify rules for the attributes of a model. Common validations include presence, length, uniqueness, and custom validations.

They do not:

  • validate previously saved data
  • prevent all occurrences of invalid data being saved to a database.

Some common validations:


validates :some_important_attribute, presence: true
validates :several, :important, :attributes, presence: true


validates :screenname, uniqueness: true

Active Record Validations on