Call Your API Using the Client Credentials Flow

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.

Auth0 makes it easy for your application to implement the Client Credentials Flow. Following successful authentication, the application will have access to an access token, which can be used to call your protected APIs. To learn more about access tokens, read Access Tokens.

Prerequisites

Before beginning this tutorial:

Register your API with Auth0
- Add appropriate API permissions
Register the M2M Application with Auth0.
- Select an Application Type of Machine to Machine Applications.
- Choose your previously-registered API.
- Authorize the M2M Application to call your API.

Steps

Request tokens: From the authorized application, request an access token for your API.
Call API: Use the retrieved access token to call your API.

Optional: Explore 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.

Example POST to token URL

cURL
C#
Go
Java
Node.JS
Obj-C
...
- PHP
- Python
- Ruby
- Swift

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

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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);

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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))

}

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HttpResponse<String> 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();

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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);
});

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#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];

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$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;
}

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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"))

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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

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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()

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Parameters

Parameter Name	Description
`grant_type`	Set this to "client_credentials".
`client_id`	Your application's Client ID. You can find this value on the application's settings tab.
`client_secret`	Your application's Client Secret. You can find this value on the application's settings tab. To learn more about available application authentication methods, read Application Credentials.
`audience`	The audience for the token, which is your API. You can find this in the Identifier field on your API's settings tab.

Response

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

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

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Validate your tokens before saving them. To learn how, read Validate ID Tokens and Validate Access Tokens.

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.

cURL
C#
Go
Java
Node.JS
Obj-C
...
- PHP
- Python
- Ruby
- Swift

curl --request GET \
  --url https://myapi.com/api \
  --header 'authorization: Bearer ACCESS_TOKEN' \
  --header 'content-type: application/json'

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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);

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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))

}

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HttpResponse<String> response = Unirest.get("https://myapi.com/api")
  .header("content-type", "application/json")
  .header("authorization", "Bearer ACCESS_TOKEN")
  .asString();

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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);
});

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#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];

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$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;
}

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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"))

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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

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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()

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Sample use cases

Customize tokens

You can use 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.

View sample application: server client + API

For a sample implementation, read the Server Client + API architecture scenario. This series of tutorials is accompanied by a code sample that you can access in GitHub.

Once your API receives a request with an access token, it will need to validate the token. To learn more, read Validate Access Tokens.

Get Started

Call Your API Using the Client Credentials Flow

Prerequisites

Steps

Request tokens

Example POST to token URL

Parameters

Response

Call API

Sample use cases

Customize tokens

View sample application: server client + API

Learn more