Header

Defines a header parameter for an API endpoint, allowing for custom validation, aliases, and metadata for OpenAPI documentation. It supports automatic conversion of underscores to hyphens and provides extensive configuration for data constraints and schema examples.

def Header(
    default: Any = Undefined,
    default_factory: Callable[[], Any] | None = _Unset,
    alias: str | None = null,
    alias_priority: int | None = _Unset,
    validation_alias: str | AliasPath | AliasChoices | None = null,
    serialization_alias: str | None = null,
    convert_underscores: bool = true,
    title: str | None = null,
    description: str | None = null,
    gt: float | None = null,
    ge: float | None = null,
    lt: float | None = null,
    le: float | None = null,
    min_length: int | None = null,
    max_length: int | None = null,
    pattern: str | None = null,
    regex: str | None = null,
    discriminator: str | None = null,
    strict: bool | None = _Unset,
    multiple_of: float | None = _Unset,
    allow_inf_nan: bool | None = _Unset,
    max_digits: int | None = _Unset,
    decimal_places: int | None = _Unset,
    examples: list[Any] | None = null,
    example: Any | None = _Unset,
    openapi_examples: dict[str, Example] | None = null,
    deprecated: deprecated | str | bool | None = null,
    include_in_schema: bool = true,
    json_schema_extra: dict[str, Any] | None = null
) - > Any

Defines an HTTP header parameter for a path operation, allowing for validation, metadata, and automatic underscore-to-hyphen conversion.

Parameters

Name	Type	Description
default	Any = Undefined	Default value if the parameter field is not set.
default_factory	`Callable[[], Any]	None` = _Unset
alias	`str	None` = null
alias_priority	`int	None` = _Unset
validation_alias	`str	AliasPath
serialization_alias	`str	None` = null
convert_underscores	bool = true	Automatically convert underscores to hyphens in the parameter field name to match standard HTTP header naming conventions.
title	`str	None` = null
description	`str	None` = null
gt	`float	None` = null
ge	`float	None` = null
lt	`float	None` = null
le	`float	None` = null
min_length	`int	None` = null
max_length	`int	None` = null
pattern	`str	None` = null
regex	`str	None` = null
discriminator	`str	None` = null
strict	`bool	None` = _Unset
multiple_of	`float	None` = _Unset
allow_inf_nan	`bool	None` = _Unset
max_digits	`int	None` = _Unset
decimal_places	`int	None` = _Unset
examples	`list[Any]	None` = null
example	`Any	None` = _Unset
openapi_examples	`dict[str, Example]	None` = null
deprecated	`deprecated	str
include_in_schema	bool = true	Whether to include this header parameter in the generated OpenAPI documentation.
json_schema_extra	`dict[str, Any]	None` = null

Returns

Type	Description
Any	A parameter metadata object used by FastAPI to extract and validate header data from the request.