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Pydantic · Type Alias

BeforeValidator

BeforeValidator runs a function before Pydantic validates a value against its annotated type. Use it to normalize raw input, then return the value for normal validation.

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Syntax

BeforeValidator(func)

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  • AfterValidator
  • PlainValidator
  • WrapValidator
  • field_validator
  • Before validators

Source: Functional Validators | Pydantic Docs. Checked 2026-11-03.