# Form Models

You can use **Pydantic models** to declare **form fields** in FastAPI.

:::callout{intent="note"}
To use forms, first install [`python-multipart`](https://github.com/Kludex/python-multipart).

Add it to your project:

```console
$ uv add python-multipart
```
:::

:::callout{intent="note"}
This is supported since FastAPI version `0.113.0`. 🤓
:::

## Pydantic Models for Forms

You just need to declare a **Pydantic model** with the fields you want to receive as **form fields**, and then declare the parameter as `Form`:

```python
from typing import Annotated

from fastapi import FastAPI, Form
from pydantic import BaseModel

app = FastAPI()


class FormData(BaseModel):
    username: str
    password: str


@app.post("/login/")
async def login(data: Annotated[FormData, Form()]):
    return data
```

**FastAPI** will **extract** the data for **each field** from the **form data** in the request and give you the Pydantic model you defined.

## Check the Docs

You can verify it in the docs UI at `/docs`:

<img src="../img/tutorial/request-form-models/image01.png" alt="">

## Forbid Extra Form Fields

In some special use cases (probably not very common), you might want to **restrict** the form fields to only those declared in the Pydantic model. And **forbid** any **extra** fields.

:::callout{intent="note"}
This is supported since FastAPI version `0.114.0`. 🤓
:::

You can use Pydantic's model configuration to `forbid` any `extra` fields:

```python
from typing import Annotated

from fastapi import FastAPI, Form
from pydantic import BaseModel

app = FastAPI()


class FormData(BaseModel):
    username: str
    password: str
    model_config = {"extra": "forbid"}


@app.post("/login/")
async def login(data: Annotated[FormData, Form()]):
    return data
```

If a client tries to send some extra data, they will receive an **error** response.

For example, if the client tries to send the form fields:

- `username`: `Rick`
- `password`: `Portal Gun`
- `extra`: `Mr. Poopybutthole`

They will receive an error response telling them that the field `extra` is not allowed:

```json
{
    "detail": [
        {
            "type": "extra_forbidden",
            "loc": ["body", "extra"],
            "msg": "Extra inputs are not permitted",
            "input": "Mr. Poopybutthole"
        }
    ]
}
```

## Summary

You can use Pydantic models to declare form fields in FastAPI. 😎

## Related pages

- [About](./about-index.md)
- [Advanced User Guide](./advanced-user-guide-index.md)
- [Deployment](./deployment-index.md)
- [FastAPI](./fastapi-index.md)
- [FastAPI Docs](../index.md)
- [Features](./features-index.md)
- [How To - Recipes](./how-to-recipes-index.md)
- [Learn](./learn-index.md)
- [More](./more-index.md)
- [OpenAPI](./openapi-index.md)

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