```txt
Hello, World from Flask!
```

And if you go to <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a> you will see the response from FastAPI:

```JSON
{
    "message": "Hello World"
}

This means that you can install the new Pydantic v2, and if something fails, you can install Pydantic v1 while you fix any problems you might have, but having the latest FastAPI.

There are **tests for both Pydantic v1 and v2**, and test **coverage** is kept at **100%**.

### Changes

You can use all the same validation features and tools you use for Pydantic models, like different data types and additional validations with `Field()`.

=== "Pydantic v2"

    ```Python hl_lines="2  5-8  11"
    {!> ../../../docs_src/settings/tutorial001.py!}
    ```

=== "Pydantic v1"

    !!! info

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