> ## Documentation Index
> Fetch the complete documentation index at: https://docs-staging-quickstart-revamp.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> Learn how to call your API from a machine-to-machine (M2M) application using the Client Credentials Flow.

# Call Your API Using the Client Credentials Flow

<Callout icon="file-lines" color="#0EA5E9" iconType="regular">
  This tutorial will help you call your API from a machine-to-machine (M2M) application using the Client Credentials Flow. To learn how the flow works and why you should use it, read [Client Credentials Flow](/docs/get-started/authentication-and-authorization-flow/client-credentials-flow).
</Callout>

Auth0 makes it easy for your application to implement the Client Credentials Flow. Following successful authentication, the application will have access to an <Tooltip tip="Access Token: Authorization credential, in the form of an opaque string or JWT, used to access an API." cta="View Glossary" href="/docs/glossary?term=access+token">access token</Tooltip>, which can be used to call your protected APIs. To learn more about access tokens, read [Access Tokens](/docs/secure/tokens/access-tokens).

## Prerequisites

**Before beginning this tutorial:**

* [Register your API with Auth0](/docs/get-started/auth0-overview/set-up-apis)

  * [Add appropriate API permissions](/docs/get-started/apis/add-api-permissions)
* [Register the M2M Application with Auth0](/docs/get-started/auth0-overview/create-applications/machine-to-machine-apps).

  * Select an **Application Type** of **Machine to Machine Applications**.
  * Choose your previously-registered API.
  * Authorize the M2M Application to call your API.

## Steps

1. [Request tokens](#request-tokens):
   From the authorized application, request an access token for your API.
2. [Call API](#call-api):
   Use the retrieved access token to call your API.

Optional: [Explore sample use cases](#sample-use-cases)

### Request tokens

To access your API, you must request an access token for it. To do so, you will need to `POST` to the [token URL](https://auth0.com/docs/api/authentication#client-credentials).

#### Example POST to token URL

<CodeGroup>
  ```bash cURL lines
  curl --request POST \
    --url 'https://{yourDomain}/oauth/token' \
    --header 'content-type: application/x-www-form-urlencoded' \
    --data grant_type=client_credentials \
    --data client_id=YOUR_CLIENT_ID \
    --data client_secret=YOUR_CLIENT_SECRET \
    --data audience=YOUR_API_IDENTIFIER
  ```

  ```csharp C# lines
  var client = new RestClient("https://{yourDomain}/oauth/token");
  var request = new RestRequest(Method.POST);
  request.AddHeader("content-type", "application/x-www-form-urlencoded");
  request.AddParameter("application/x-www-form-urlencoded", "grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET&audience=YOUR_API_IDENTIFIER", ParameterType.RequestBody);
  IRestResponse response = client.Execute(request);
  ```

  ```go Go lines expandable
  package main

  import (
  	"fmt"
  	"strings"
  	"net/http"
  	"io/ioutil"
  )

  func main() {

  	url := "https://{yourDomain}/oauth/token"

  	payload := strings.NewReader("grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET&audience=YOUR_API_IDENTIFIER")

  	req, _ := http.NewRequest("POST", url, payload)

  	req.Header.Add("content-type", "application/x-www-form-urlencoded")

  	res, _ := http.DefaultClient.Do(req)

  	defer res.Body.Close()
  	body, _ := ioutil.ReadAll(res.Body)

  	fmt.Println(res)
  	fmt.Println(string(body))

  }
  ```

  ```java Java lines
  HttpResponse response = Unirest.post("https://{yourDomain}/oauth/token")
    .header("content-type", "application/x-www-form-urlencoded")
    .body("grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET&audience=YOUR_API_IDENTIFIER")
    .asString();
  ```

  ```javascript Node.JS lines
  var axios = require("axios").default;

  var options = {
    method: 'POST',
    url: 'https://{yourDomain}/oauth/token',
    headers: {'content-type': 'application/x-www-form-urlencoded'},
    data: new URLSearchParams({
      grant_type: 'client_credentials',
      client_id: 'YOUR_CLIENT_ID',
      client_secret: 'YOUR_CLIENT_SECRET',
      audience: 'YOUR_API_IDENTIFIER'
    })
  };

  axios.request(options).then(function (response) {
    console.log(response.data);
  }).catch(function (error) {
    console.error(error);
  });
  ```

  ```obj-c Obj-C lines expandable
  #import <Foundation/Foundation.h>

  NSDictionary *headers = @{ @"content-type": @"application/x-www-form-urlencoded" };

  NSMutableData *postData = [[NSMutableData alloc] initWithData:[@"grant_type=client_credentials" dataUsingEncoding:NSUTF8StringEncoding]];
  [postData appendData:[@"&client_id=YOUR_CLIENT_ID" dataUsingEncoding:NSUTF8StringEncoding]];
  [postData appendData:[@"&client_secret=YOUR_CLIENT_SECRET" dataUsingEncoding:NSUTF8StringEncoding]];
  [postData appendData:[@"&audience=YOUR_API_IDENTIFIER" dataUsingEncoding:NSUTF8StringEncoding]];

  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"https://{yourDomain}/oauth/token"]
                                                         cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                     timeoutInterval:10.0];
  [request setHTTPMethod:@"POST"];
  [request setAllHTTPHeaderFields:headers];
  [request setHTTPBody:postData];

  NSURLSession *session = [NSURLSession sharedSession];
  NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request
                                              completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
                                                  if (error) {
                                                      NSLog(@"%@", error);
                                                  } else {
                                                      NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *) response;
                                                      NSLog(@"%@", httpResponse);
                                                  }
                                              }];
  [dataTask resume];
  [dataTask resume];
  ```

  ```php PHP lines expandable
  $curl = curl_init();

  curl_setopt_array($curl, [
    CURLOPT_URL => "https://{yourDomain}/oauth/token",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_POSTFIELDS => "grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET&audience=YOUR_API_IDENTIFIER",
    CURLOPT_HTTPHEADER => [
      "content-type: application/x-www-form-urlencoded"
    ],
  ]);

  $response = curl_exec($curl);
  $err = curl_error($curl);

  curl_close($curl);

  if ($err) {
    echo "cURL Error #:" . $err;
  } else {
    echo $response;
  }
  ```

  ```python Python lines
  import http.client

  conn = http.client.HTTPSConnection("")

  payload = "grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET&audience=YOUR_API_IDENTIFIER"

  headers = { 'content-type': "application/x-www-form-urlencoded" }

  conn.request("POST", "/{yourDomain}/oauth/token", payload, headers)

  res = conn.getresponse()
  data = res.read()

  print(data.decode("utf-8"))
  ```

  ```ruby Ruby lines
  require 'uri'
  require 'net/http'
  require 'openssl'

  url = URI("https://{yourDomain}/oauth/token")

  http = Net::HTTP.new(url.host, url.port)
  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE

  request = Net::HTTP::Post.new(url)
  request["content-type"] = 'application/x-www-form-urlencoded'
  request.body = "grant_type=client_credentials&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET&audience=YOUR_API_IDENTIFIER"

  response = http.request(request)
  puts response.read_body
  ```

  ```swift Swift lines expandable
  import Foundation

  let headers = ["content-type": "application/x-www-form-urlencoded"]

  let postData = NSMutableData(data: "grant_type=client_credentials".data(using: String.Encoding.utf8)!)
  postData.append("&client_id=YOUR_CLIENT_ID".data(using: String.Encoding.utf8)!)
  postData.append("&client_secret=YOUR_CLIENT_SECRET".data(using: String.Encoding.utf8)!)
  postData.append("&audience=YOUR_API_IDENTIFIER".data(using: String.Encoding.utf8)!)

  let request = NSMutableURLRequest(url: NSURL(string: "https://{yourDomain}/oauth/token")! as URL,
                                          cachePolicy: .useProtocolCachePolicy,
                                      timeoutInterval: 10.0)
  request.httpMethod = "POST"
  request.allHTTPHeaderFields = headers
  request.httpBody = postData as Data

  let session = URLSession.shared
  let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
    if (error != nil) {
      print(error)
    } else {
      let httpResponse = response as? HTTPURLResponse
      print(httpResponse)
    }
  })

  dataTask.resume()
  ```
</CodeGroup>

##### Parameters

<table class="table">
  <thead>
    <tr>
      <th>Parameter Name</th>
      <th>Description</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td><code>grant\_type</code></td>
      <td>Set this to "client\_credentials".</td>
    </tr>

    <tr>
      <td><code>client\_id</code></td>
      <td>Your application's Client ID. You can find this value on the <a href="https://manage.auth0.com/#/applications">application's settings tab</a>.</td>
    </tr>

    <tr>
      <td><code>client\_secret</code></td>
      <td>Your application's Client Secret. You can find this value on the <a href="https://manage.auth0.com/#/applications">application's settings tab</a>.  To learn more about available application authentication methods, read <a href="/docs/secure/application-credentials">Application Credentials</a>.</td>
    </tr>

    <tr>
      <td><code>audience</code></td>
      <td>The audience for the token, which is your API. You can find this in the <strong>Identifier</strong> field on your <a href="https://manage.auth0.com/#/apis">API's settings tab</a>.</td>
    </tr>

    <tr>
      <td><code>organization</code></td>
      <td>Optional. The organization name or identifier you want the request to be associated with. To learn more, read <a href="/docs/manage-users/organizations/organizations-for-m2m-applications">Machine-to-Machine Access for Organizations</a>.</td>
    </tr>
  </tbody>
</table>

#### Response

If all goes well, you'll receive an `HTTP 200` response with a payload containing `access_token`, `token_type`, and `expires_in` values:

```json lines
{
  "access_token":"eyJz93a...k4laUWw",
  "token_type":"Bearer",
  "expires_in":86400
}
```

<Warning>
  Validate your tokens before saving them. To learn how, read [Validate ID Tokens](/docs/secure/tokens/id-tokens/validate-id-tokens) and [Validate Access Tokens](/docs/secure/tokens/access-tokens/validate-access-tokens).
</Warning>

### Call API

To call your API from the M2M application, the application must pass the retrieved access token as a Bearer token in the Authorization header of your HTTP request.

<CodeGroup>
  ```bash cURL lines
  curl --request GET \
    --url https://myapi.com/api \
    --header 'authorization: Bearer ACCESS_TOKEN' \
    --header 'content-type: application/json'
  ```

  ```csharp C# lines
  var client = new RestClient("https://myapi.com/api");
  var request = new RestRequest(Method.GET);
  request.AddHeader("content-type", "application/json");
  request.AddHeader("authorization", "Bearer ACCESS_TOKEN");
  IRestResponse response = client.Execute(request);
  ```

  ```go Go lines expandable
  package main

  import (
  	"fmt"
  	"net/http"
  	"io/ioutil"
  )

  func main() {

  	url := "https://myapi.com/api"

  	req, _ := http.NewRequest("GET", url, nil)

  	req.Header.Add("content-type", "application/json")
  	req.Header.Add("authorization", "Bearer ACCESS_TOKEN")

  	res, _ := http.DefaultClient.Do(req)

  	defer res.Body.Close()
  	body, _ := ioutil.ReadAll(res.Body)

  	fmt.Println(res)
  	fmt.Println(string(body))

  }
  ```

  ```java Java lines
  HttpResponse response = Unirest.get("https://myapi.com/api")
    .header("content-type", "application/json")
    .header("authorization", "Bearer ACCESS_TOKEN")
    .asString();
  ```

  ```javascript Node.JS lines
  var axios = require("axios").default;

  var options = {
    method: 'GET',
    url: 'https://myapi.com/api',
    headers: {'content-type': 'application/json', authorization: 'Bearer ACCESS_TOKEN'}
  };

  axios.request(options).then(function (response) {
    console.log(response.data);
  }).catch(function (error) {
    console.error(error);
  });
  ```

  ```obj-c Obj-C lines
  #import <Foundation/Foundation.h>

  NSDictionary *headers = @{ @"content-type": @"application/json",
                             @"authorization": @"Bearer ACCESS_TOKEN" };

  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"https://myapi.com/api"]
                                                         cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                     timeoutInterval:10.0];
  [request setHTTPMethod:@"GET"];
  [request setAllHTTPHeaderFields:headers];

  NSURLSession *session = [NSURLSession sharedSession];
  NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request
                                              completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
                                                  if (error) {
                                                      NSLog(@"%@", error);
                                                  } else {
                                                      NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *) response;
                                                      NSLog(@"%@", httpResponse);
                                                  }
                                              }];
  [dataTask resume];
  ```

  ```php PHP lines expandable
  $curl = curl_init();

  curl_setopt_array($curl, [
    CURLOPT_URL => "https://myapi.com/api",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "GET",
    CURLOPT_HTTPHEADER => [
      "authorization: Bearer ACCESS_TOKEN",
      "content-type: application/json"
    ],
  ]);

  $response = curl_exec($curl);
  $err = curl_error($curl);

  curl_close($curl);

  if ($err) {
    echo "cURL Error #:" . $err;
  } else {
    echo $response;
  }
  ```

  ```python Python lines
  import http.client

  conn = http.client.HTTPSConnection("myapi.com")

  headers = {
      'content-type': "application/json",
      'authorization': "Bearer ACCESS_TOKEN"
      }

  conn.request("GET", "/api", headers=headers)

  res = conn.getresponse()
  data = res.read()

  print(data.decode("utf-8"))
  ```

  ```ruby Ruby lines
  require 'uri'
  require 'net/http'
  require 'openssl'

  url = URI("https://myapi.com/api")

  http = Net::HTTP.new(url.host, url.port)
  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE

  request = Net::HTTP::Get.new(url)
  request["content-type"] = 'application/json'
  request["authorization"] = 'Bearer ACCESS_TOKEN'

  response = http.request(request)
  puts response.read_body
  ```

  ```swift Swift lines
  import Foundation

  let headers = [
    "content-type": "application/json",
    "authorization": "Bearer ACCESS_TOKEN"
  ]

  let request = NSMutableURLRequest(url: NSURL(string: "https://myapi.com/api")! as URL,
                                          cachePolicy: .useProtocolCachePolicy,
                                      timeoutInterval: 10.0)
  request.httpMethod = "GET"
  request.allHTTPHeaderFields = headers

  let session = URLSession.shared
  let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
    if (error != nil) {
      print(error)
    } else {
      let httpResponse = response as? HTTPURLResponse
      print(httpResponse)
    }
  })

  dataTask.resume()
  ```
</CodeGroup>

### Sample use cases

#### Customize tokens

You can use [Actions](/docs/customize/actions) to deny access tokens based on custom logic and/or add claims to access tokens. Auth0 invokes Actions attached to the client credentials grant at runtime to execute your custom logic.

To learn more, read about the Actions [Machine to Machine Flow](/docs/customize/actions/explore-triggers/machine-to-machine-trigger).

#### View sample application: server client + API

For a sample implementation, read the [Server Client + API](/docs/get-started/architecture-scenarios/server-application-api) architecture scenario. This series of tutorials is accompanied by a [code sample that you can access in GitHub](https://github.com/auth0-samples/auth0-pnp-exampleco-timesheets).

Once your API receives a request with an access token, it will need to validate the token. To learn more, read [Validate Access Tokens](/docs/secure/tokens/access-tokens/validate-access-tokens).

## Learn more

* [Machine to Machine Triggers](/docs/customize/actions/explore-triggers/machine-to-machine-trigger)
* [OpenID Connect Protocol](/docs/authenticate/protocols/openid-connect-protocol)
* [Tokens](/docs/secure/tokens)