title: node js with gmail api, The API returned an error: Error: unauthorized_client
body: <p>Edit:
  The error is happening on on this piece of code:</p>
  
  <pre><code>   var gmail = google.gmail('v1');
        gmail.users.labels.list({
          auth: auth,
          userId: 'me',
        }, function(err, response) {
          if (err) {
            console.log('The API returned an error: ' + err);
            return;
          }
  </code></pre>
  
  <p>I am using gmail api with Node js. When I go through their quickstart guide I keep getting this error. </p>
  
  <p><a href="https://developers.google.com/gmail/api/quickstart/nodejs" rel="noreferrer">https://developers.google.com/gmail/api/quickstart/nodejs</a></p>
  
  <pre><code> The API returned an error: Error: unauthorized_client
  </code></pre>
  
  <p>Keep in mind, I went through the quickstart with my email adress, everything was fine. No errors at all. I decided to create a dummy email for test purposes. The only change I made was <code>step 1-g</code> switching out the <code>client_secret.json</code> files to hold the new credentials and key. I tried switching back to my old file but, the error still persists. </p>
  
  <p>At the bottom of the page in the link provided it states.</p>
  
  <pre><code>Authorization information is stored on the file system, so subsequent executions will not prompt for authorization. Would I have to clear or refresh the information? If so how can I do this?
  </code></pre>
  
  <p>If it helps I will repost all the code in my quickstart.js file. </p>
  
  <pre><code>var fs = require('fs');
  var readline = require('readline');
  var google = require('googleapis');
  var googleAuth = require('google-auth-library');
  
  var SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];
  var TOKEN_DIR = (process.env.HOME || process.env.HOMEPATH ||
      process.env.USERPROFILE) + '/.credentials/';
  var TOKEN_PATH = TOKEN_DIR + 'gmail-nodejs-quickstart.json';
  
  // Load client secrets from a local file.
  fs.readFile('client_secret.json', function processClientSecrets(err, content) {
    if (err) {
      console.log('Error loading client secret file: ' + err);
      return;
    }
    // Authorize a client with the loaded credentials, then call the
    // Gmail API.
    authorize(JSON.parse(content), listLabels);
  });
  
  /**
   * Create an OAuth2 client with the given credentials, and then execute the
   * given callback function.
   *
   * @param {Object} credentials The authorization client credentials.
   * @param {function} callback The callback to call with the authorized client.
   */
  function authorize(credentials, callback) {
    var clientSecret = credentials.installed.client_secret;
    var clientId = credentials.installed.client_id;
    var redirectUrl = credentials.installed.redirect_uris[0];
    var auth = new googleAuth();
    var oauth2Client = new auth.OAuth2(clientId, clientSecret, redirectUrl);
  
    // Check if we have previously stored a token.
    fs.readFile(TOKEN_PATH, function(err, token) {
      if (err) {
        getNewToken(oauth2Client, callback);
      } else {
        oauth2Client.credentials = JSON.parse(token);
        callback(oauth2Client);
      }
    });
  }
  
  /**
   * Get and store new token after prompting for user authorization, and then
   * execute the given callback with the authorized OAuth2 client.
   *
   * @param {google.auth.OAuth2} oauth2Client The OAuth2 client to get token for.
   * @param {getEventsCallback} callback The callback to call with the authorized
   *     client.
   */
  function getNewToken(oauth2Client, callback) {
    var authUrl = oauth2Client.generateAuthUrl({
      access_type: 'offline',
      scope: SCOPES
    });
    console.log('Authorize this app by visiting this url: ', authUrl);
    var rl = readline.createInterface({
      input: process.stdin,
      output: process.stdout
    });
    rl.question('Enter the code from that page here: ', function(code) {
      rl.close();
      oauth2Client.getToken(code, function(err, token) {
        if (err) {
          console.log('Error while trying to retrieve access token', err);
          return;
        }
        oauth2Client.credentials = token;
        storeToken(token);
        callback(oauth2Client);
      });
    });
  }
  
  /**
   * Store token to disk be used in later program executions.
   *
   * @param {Object} token The token to store to disk.
   */
  function storeToken(token) {
    try {
      fs.mkdirSync(TOKEN_DIR);
    } catch (err) {
      if (err.code != 'EEXIST') {
        throw err;
      }
    }
    fs.writeFile(TOKEN_PATH, JSON.stringify(token));
    console.log('Token stored to ' + TOKEN_PATH);
  }
  
  /**
   * Lists the labels in the user's account.
   *
   * @param {google.auth.OAuth2} auth An authorized OAuth2 client.
   */
  function listLabels(auth) {
    var gmail = google.gmail('v1');
    gmail.users.labels.list({
      auth: auth,
      userId: 'me',
    }, function(err, response) {
      if (err) {
        console.log('The API returned an error: ' + err);
        return;
      }
      var labels = response.labels;
      if (labels.length == 0) {
        console.log('No labels found.');
      } else {
        console.log('Labels:');
        for (var i = 0; i &lt; labels.length; i++) {
          var label = labels[i];
          console.log('- %s', label.name);
        }
      }
    });
  }
  </code></pre>