Omitted bool and bool | None form fields now use their declared defaults or produce missing-field errors, consistent with other fields and Pydantic behavior. FastAPI no longer infers False for omitted booleans. This applies to individual form parameters, form models, and unions of form models. Omitted boolean model fields are excluded from model_dump(exclude_unset=True), and their defaults no longβ¦
Fixes π Fix OpenAPI schemas for standalone nullable form unions. PR #16598 by @tiangolo.
Features β¨ Add support for combining unions of form models. PR #16596 by @tiangolo.
Query, header, cookie, and form parameter models now apply their extra configuration to all submitted fields in the same parameter location, consistent with Pydantic behavior. This includes fields declared in other models, individual parameters, or dependencies, which were previously excluded. With extra="forbid", fields outside the model are rejected even if another parameter declares them. Withβ¦
Features β¨ Add support for optional unions of form models. PR #16586 by @tiangolo.
Features β¨ Add support for optional query, header, and cookie parameter models. PR #16584 by @tiangolo.
Features β¨ Add support for optional form models. PR #16582 by @tiangolo.
Fixes π Preserve form media types in OpenAPI. PR #16579 by @tiangolo.
Features β¨ Add support for combining form models. PR #16577 by @tiangolo.
Features β¨ Add support for combining query, header, and cookie parameter models. PR #16573 by @tiangolo. Docs π Clarify boolean query parameter parsing. PR #16569 by @tiangolo. π Clarify nullable query parameters and path parameter defaults. PR #16568 by @tiangolo. Internal π· Remove translation notifications and approval labeling. PR #16570 by @tiangolo.
Fixes π Preserve uploaded file positions when converting to bytes. PR #16566 by @tiangolo.
Fixes π Fix validation error locations for form and file AliasChoices. PR #16564 by @tiangolo.
Fixes π Respect model alias settings for query, header, and cookie parameters. PR #16562 by @tiangolo.
Fixes π Fix AliasChoices for path parameters. PR #16560 by @tiangolo.
Fixes π Fix AliasChoices for named JSON body parameters. PR #16559 by @tiangolo. π Fix AliasChoices extraction for form models. PR #16557 by @tiangolo.
Fixes π Fix AliasChoices for query parameters, headers, and cookies. PR #16555 by @tiangolo.
Fixes π Preserve Pydantic field metadata in inferred request parameters. PR #16553 by @tiangolo.
Fixes π Preserve Pydantic field metadata when request options are omitted. PR #16549 by @tiangolo.
Fixes π Preserve Pydantic Field() attributes in request parameters. PR #16547 by @tiangolo.
The deprecated **extra keyword arguments have been removed from Path, Query, Header, Cookie, Body, Form, and File. Unknown keyword arguments now raise TypeError. For additional JSON Schema properties, replace, for example, Query(custom="value") with Query(json_schema_extra={"custom": "value"}). Breaking Changes π₯ Remove deprecated **extra from request parameters. PR #16545 by @tiangolo.
Features β¨ Add Pydantic validation options to request parameters. PR #16542 by @tiangolo.
Unions of form models now apply the same browser form handling as individual models. Empty scalar fields use defaults or produce missing-field errors, empty list items are preserved, omitted boolean fields become False, and unselected files are treated as missing. JSON request bodies are unchanged. Fixes π Apply browser form handling to unions of Pydantic models. PR #16540 by @tiangolo.
Validation errors for header parameter models now report the HTTP header name, such as int-val, instead of the Python field name, int_val. Explicit aliases, Header(convert_underscores=False), and Pydantic models with loc_by_alias=False keep their existing behavior. Fixes π Fix header model validation errors to report HTTP header names. PR #16538 by @tiangolo.
JSON request bodies now distinguish an explicit null from an omitted value. For individual Body parameters, null is validated as None: nullable types accept it, and non-nullable types reject it even when a default is defined. Defaults and default factories apply only when the value is omitted. This applies both to parameters inside JSON objects and to parameters representing the entire body. Clienβ¦
When no file is selected, browsers submit a file part with an empty filename and empty content. FastAPI now treats this as missing: required file fields return a validation error, and fields with defaults or default factories use them. Unselected inputs are ignored in lists of files. Named zero-byte files are still accepted. Breaking Changes π Treat unselected browser file inputs as missing. PR #1β¦
Browsers submit empty text inputs as empty strings (""). FastAPI now treats empty scalar form values as missing in form models, matching individual Form parameters. Required fields return a validation error. Fields with defaults or default factories use them and remain unset in model_dump(exclude_unset=True). Empty strings inside lists are preserved. Omitted boolean form fields still become False.β¦
Defaults for omitted Query, Header, Cookie, and Form parameters and model fields are no longer treated as user input. Defaults are not validated unless validate_default=True is enabled. If you rely on validators running for omitted values, enable default validation with Field(validate_default=True) for model fields or, for example, Query(validate_default=True) for individual parameters. Body(validβ¦
Omitted bool and bool | None form fields are now interpreted as False, matching unchecked HTML checkboxes. This applies to individual Form parameters and form models, including required fields and fields with defaults of True or None. The inferred value is considered explicitly set, including in model_dump(exclude_unset=True). JSON requests and direct Pydantic validation are unchanged. See Booleanβ¦
The root_path parameter in FastAPI() is deprecated. Configure the server with fastapi run --root-path /api/v1 instead. Breaking Changes ποΈ Deprecate the root_path parameter in FastAPI. PR #16520 by @tiangolo.
Breaking Changes π₯ Remove deprecated openapi_prefix and unused **extra from FastAPI. PR #16518 by @tiangolo. Docs π Document URL paths in templates. PR #16517 by @tiangolo.