# Requests and Responses

The Strapi back end server is based on . When you send requests through the [REST API](/cms/api/rest), a context object (`ctx`) is passed to every element of the Strapi back end (e.g., [policies](/cms/backend-customization/policies), [controllers](/cms/backend-customization/controllers), [services](/cms/backend-customization/services)).

`ctx` includes 3 main objects:

- [`ctx.request`](#ctxrequest) for information about the request sent by the client making an API request,
- [`ctx.state`](#ctxstate) for information about the state of the request within the Strapi back end,
- and [`ctx.response`](#ctxresponse) for information about the response that the server will return.

:::tip
The request's context can also be accessed from anywhere in the code with the [`strapi.requestContext` function](#accessing-the-request-context-anywhere).
:::

:::info
In addition to the concepts and parameters described in the following documentation, you might find additional information in the ,  and .
:::

<figure style={{width: '100%', margin: '0'}}>
  <img src="/img/assets/backend-customization/diagram-requests-responses.png" alt="Simplified Strapi backend diagram with requests and responses highlighted" />
  <em><figcaption style={{fontSize: '12px'}}>The diagram represents a simplified version of how a request travels through the Strapi back end, with requests and responses highlighted. The backend customization introduction page includes a complete, <a href="/cms/backend-customization#interactive-diagram">interactive diagram</a>.</figcaption></em>
</figure>

## `ctx.request`

The `ctx.request` object contains the following parameters:

| Parameter             | Description                                                                                  | Type     |
| --------------------- | -------------------------------------------------------------------------------------------- | -------- |
| `ctx.request.body`    | Parsed version of the body. | `Object` |
| `ctx.request.files`   | Files sent with the request. | `Array` |
| `ctx.request.headers` | Headers sent with the request. | `Object` |
| `ctx.request.host`    | Host part of the URL, including the port. | `String` |
| `ctx.request.hostname`| Host part of the URL, excluding the port. | `String` |
| `ctx.request.href`    | Complete URL of the requested resource, including the protocol, domain, port (if specified), path, and query parameters. | `String` |
| `ctx.request.ip`      | IP of the person sending the request.| `String` |
| `ctx.request.ips`     | When `X-Forwarded-For` is present and `app.proxy` is enabled, an array of IPs is returned, ordered from upstream to downstream. <br /><br />For example if the value were "client, proxy1, proxy2", you would receive the `["client", "proxy1", "proxy2"]` array. | `Array` |
| `ctx.request.method`  | Request method (e.g., `GET`, `POST`). | `String` |
| `ctx.request.origin`  | URL part before the first `/`. | `String` |
| `ctx.request.params`  | Parameters sent in the URL.<br /><br/>For example, if the internal URL is `/restaurants/:id`, whatever you replace `:id` in the real request becomes accessible through `ctx.request.params.id`. | `Object` |
| `ctx.request.path`    | Path of the requested resource, excluding the query parameters. | `String` |
| `ctx.request.protocol`| Protocol being used (e.g., `https` or `http`). | `String` |
| `ctx.request.query`   | Strapi-specific [query parameters](#ctxrequestquery). | `Object` |
| `ctx.request.subdomains`| Subdomains included in the URL.<br /><br />For example, if the domain is `tobi.ferrets.example.com`, the value is the following array: `["ferrets", "tobi"]`. | `Array` |
| `ctx.request.url`     | Path and query parameters of the requested resource, excluding the protocol, domain, and port. | `String` |

<details>
<summary>Differences between protocol, origin, url, href, path, host, and hostname :</summary>

Given an API request sent to the `https://example.com:1337/api/restaurants?id=123` URL, here is what different parameters of the `ctx.request` object return:

| Parameter  | Returned value                                    |
| ---------- | ------------------------------------------------- |
| `ctx.request.href`     | `https://example.com:1337/api/restaurants?id=123` |
| `ctx.request.protocol` | `https`                                           |
| `ctx.request.host`     | `localhost:1337`                                  |
| `ctx.request.hostname` | `localhost`                                       |
| `ctx.request.origin`   | `https://example.com:1337`                          |
| `ctx.request.url`      | `/api/restaurants?id=123`                         |
| `ctx.request.path`     | `/api/restaurants`                                |

</details>

### `ctx.request.query`

`ctx.request` provides a `query` object that gives access to Strapi query parameters. The following table lists available parameters with a short description and a link to the relevant REST API documentation section (see [REST API parameters](/cms/api/rest/parameters) for more information):

| Parameter | Description                                                                                                                                            | Type                 |
| -------------------------------------| --------------------------------------------------------------------------------------------------------------------------- | -------------------- |
| `ctx.request.query`<br />`ctx.query` | The whole query object.                                                                                                    | `Object`             |
| `ctx.request.query.sort`             | Parameters to [sort the response](/cms/api/rest/sort-pagination.md#sorting)                                            | `String` or `Array`  |
| `ctx.request.query.filters`          | Parameters to [filter the response](/cms/api/rest/filters)                                | `Object`             |
| `ctx.request.query.populate`         | Parameters to [populate relations, components, or dynamic zones](/cms/api/rest/populate-select#population)             | `String` or `Object` |
| `ctx.request.query.fields`           | Parameters to [select only specific fields to return with the response](/cms/api/rest/populate-select#field-selection) | `Array`              |
| `ctx.request.query.pagination`       | Parameter to [page through entries](/cms/api/rest/sort-pagination.md#pagination)                                       | `Object`             |
| `ctx.request.query.publicationState` | Parameter to [select the Draft & Publish state](/cms/api/rest/status)            | `String`             |
| `ctx.request.query.locale`           | Parameter to [select one or multiple locales](/cms/api/rest/locale)                         | `String` or `Array`  |

## `ctx.state`

The `ctx.state` object gives access to the state of the request within the Strapi back end, including specific values about the [user](#ctxstateuser), [authentication](#ctxstateauth), [route](#ctxstateroute):

| Parameter                  | Description                                                                 | Type     |
| ---------------------------|---------------------------------------------------------------------------- | -------- |
| `ctx.state.isAuthenticated`| Returns whether the current user is authenticated in any way.               | `Boolean` |

### `ctx.state.user`

The `ctx.state.user` object gives access to information about the user performing the request and includes the following parameters:

| Parameter | Description                                                                                  | Type     |
| ----------| -------------------------------------------------------------------------------------------- | -------- |
| `ctx.state.user`| User's information. Only one relation is populated.                   | `Object` |
| `ctx.state.user.role`| The user's role | `Object` |
<!-- which type of "user" are we talking about here? a "U&P"-related user? -->

### `ctx.state.auth`

The `ctx.state.auth` object gives access to information related to the authentication and includes the following parameters:

| Parameter                     | Description                                                                                  | Type     |
| ------------------------------| -------------------------------------------------------------------------------------------- | -------- |
| `ctx.state.auth.strategy`     | Information about the currently used authentication strategy ([Users & Permissions plugin](/cms/features/users-permissions) or [API tokens](/cms/features/api-tokens)) | `Object` |
| `ctx.state.auth.strategy.name`| Name of the currently used strategy                                                          | `String` |
| `ctx.state.auth.credentials`  | The user's credentials                                                                      | `String` |
<!-- ? ctx.state.auth.strategy seems to include the authenticate and verify functions. should we document them somewhere? -->
<!-- ? not sure what credentials are used for ? -->

### `ctx.state.route`

The `ctx.state.route` object gives access to information related to the current route and includes the following parameters:

| Parameter | Description                                                                                  | Type     |
| ----------| -------------------------------------------------------------------------------------------- | -------- |
| `ctx.state.route.method`| Method used to access the current route. | `String` |
| `ctx.state.route.path`| Path of the current route. | `String` |
| `ctx.state.route.config`| Configuration information about the current route. | `Object` |
| `ctx.state.route.handler`| Handler (controller) of the current route. | `Object` |
| `ctx.state.route.info`| Additional information about the current route, such as the apiName and the API request type. | `Object` |
| `ctx.state.route.info.apiName`| Name of the used API.  | `String` |
| `ctx.state.route.info.type`| Type of the used API. | `String` |

## `ctx.response`

The `ctx.response` object gives access to information related to the response that the server will return and includes the following parameters:

| Parameter | Description                                                                                  | Type     |
| ----------| -------------------------------------------------------------------------------------------- | -------- |
| `ctx.response.body`| Body of the response. | `Any` |
| `ctx.response.status` | Status code of the response. | `Integer` |
| `ctx.response.message`| Status message of the response.<br/><br />By default, `response.message` is associated with `response.status`. | `String` |
| `ctx.response.header`<br />`ctx.response.headers`| Header(s) sent with the response. | `Object` |
| `ctx.response.length`|  header value as a number when present, or deduces it from `ctx.body` when possible; otherwise, returns `undefined`. | `Integer` |
| `ctx.response.redirect`<br />`ctx.response.redirect(url, [alt])` | Performs a `302` redirect to the URL. The string "back" is special-cased to provide Referrer support; when Referrer is not present, alt or "/" is used.<br /><br />Example: `ctx.response.redirect('back', '/index.html');` | `Function` |
| `ctx.response.attachment`<br /><br />`ctx.response.attachment([filename], [options])` | Sets  header to "attachment" to signal the client to prompt for download. Optionally specify the filename of the download and some . | `Function` |
| `ctx.response.type`|  header, void of parameters such as "charset". | `String` |
| `ctx.response.lastModified`|  header as a Date, if it exists. | `DateTime` |
| `ctx.response.etag`| Sets the  of a response including the wrapped "s.<br/>There is no corresponding `response.etag` getter. | `String` |
<!-- I don't understand what these 5 last lines above mean, just copied and pasted them from the user's PR 🤷 — piwi -->

## Accessing the request context anywhere

Strapi exposes a way to access the current request context from anywhere in the code (e.g. lifecycle functions).

You can access the request as follows:

```js
const ctx = strapi.requestContext.get();
```

You should only use this inside of functions that will be called in the context of an HTTP request.

```js
// correct

const service = {
  myFunction() {
    const ctx = strapi.requestContext.get();
    console.log(ctx.state.user);
  },
};

// incorrect
const ctx = strapi.requestContext.get();

const service = {
  myFunction() {
    console.log(ctx.state.user);
  },
};
```

**Example:**

```js title="./api/test/content-types/article/lifecycles.js"

module.exports = {
  beforeUpdate() {
    const ctx = strapi.requestContext.get();

    console.log('User info in service: ', ctx.state.user);
  },
};
```

:::note
Strapi uses a Node.js feature called  to make the context available anywhere.
:::