<img src="/img/tutorial/behind-a-proxy/image03.png">

!!! tip
    The docs UI will interact with the server that you select.

### Disable automatic server from `root_path`

If you don't want **FastAPI** to include an automatic server using the `root_path`, you can use the parameter `root_path_in_servers=False`:

```Python hl_lines="9"

Documentation = "https://fastapi.tiangolo.com/"
Repository = "https://github.com/tiangolo/fastapi"

[project.optional-dependencies]

standard = [
    "fastapi-cli >=0.0.2",
    # For the test client
    "httpx >=0.23.0",
    # For templates
    "jinja2 >=2.11.2",
    # For forms and file uploads
    "python-multipart >=0.0.7",
    # For UJSONResponse

### Small Errors Automatically Handled

When building web APIs with FastAPI, if there's an error in our code, FastAPI will normally contain it to the single request that triggered the error. 🛡

The client will get a **500 Internal Server Error** for that request, but the application will continue working for the next requests instead of just crashing completely.

### Bigger Errors - Crashes

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,tasks: Can raise exception for dependency, handled after response is sent
    Note over client,operation: Can raise HTTPException and can change the response
    client ->> dep: Start request

* Designed around these standards, after a meticulous study. Instead of an afterthought layer on top.
* This also allows using automatic **client code generation** in many languages.

### Automatic docs

Interactive API documentation and exploration web user interfaces. As the framework is based on OpenAPI, there are multiple options, 2 included by default.

## Install `WebSockets`

First you need to install `WebSockets`:

<div class="termy">

```console
$ pip install websockets

---> 100%
```

</div>

## WebSockets client

### In production

In your production system, you probably have a frontend created with a modern framework like React, Vue.js or Angular.

  features:
  - search.suggest
  - search.highlight
  - content.tabs.link
  - navigation.indexes
  - content.tooltips
  - navigation.path
  - content.code.annotate
  - content.code.copy
  - content.code.select
  - navigation.tabs
  icon:
    repo: fontawesome/brands/github-alt
  logo: img/icon-white.svg
  favicon: img/favicon.png
  language: en
repo_name: tiangolo/fastapi
repo_url: https://github.com/tiangolo/fastapi

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.
    * If it is not, the client will see a useful, clear error.
* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`) for `GET` requests.
    * As the `q` parameter is declared with `= None`, it is optional.

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.
    * If it is not, the client will see a useful, clear error.
* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`) for `GET` requests.
    * As the `q` parameter is declared with `= None`, it is optional.