diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index ab82de3..ea3a54f 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -20,22 +20,7 @@ public function getConfigTreeBuilder()
         $treeBuilder = new TreeBuilder();
         $rootNode = $treeBuilder->root('happy_r_google_api');
 
-        $rootNode
-          ->children()
-            ->scalarNode('application_name')->isRequired()->cannotBeEmpty()->end()
-            ->scalarNode('oauth2_client_id')->isRequired()->cannotBeEmpty()->end()
-            ->scalarNode('oauth2_client_secret')->isRequired()->cannotBeEmpty()->end()
-            ->scalarNode('oauth2_redirect_uri')->isRequired()->cannotBeEmpty()->end()
-            ->scalarNode('developer_key')->isRequired()->cannotBeEmpty()->end()
-            ->scalarNode('site_name')->isRequired()->cannotBeEmpty()->end()
-
-            ->scalarNode('authClass')->end()
-            ->scalarNode('ioClass')->end()
-            ->scalarNode('cacheClass')->end()
-            ->scalarNode('basePath')->end()
-            ->scalarNode('ioFileCache_directory')->end()
-          //end rootnode children
-          ->end();
+        $this->configureAccountNode($rootNode);
 
         //let use the api defaults
         //$this->addServicesSection($rootNode);
@@ -43,7 +28,6 @@ public function getConfigTreeBuilder()
         return $treeBuilder;
     }
 
-
     /**
      * Add the service section
      *
@@ -144,4 +128,100 @@ private function addServicesSection(ArrayNodeDefinition $rootNode)
 
         ;
     }
+
+    /**
+     * Add properties and validation for account configuration.
+     *
+     * @param ArrayNodeDefinition $node
+     */
+    private function configureAccountNode(ArrayNodeDefinition $node)
+    {
+        $node
+            ->beforeNormalization()
+                ->ifTrue(function ($v) { return is_array($v) && !array_key_exists('accounts', $v) && !array_key_exists('account', $v); })
+                ->then(function ($v) {
+                    // Key that should not be rewritten to the account config
+                    $excludedKeys = array('default_account' => true);
+                    $account = array();
+
+                    foreach ($v as $key => $value) {
+                        if (isset($excludedKeys[$key])) {
+                            continue;
+                        }
+
+                        $account[$key] = $v[$key];
+                        unset($v[$key]);
+                    }
+
+                    $v['default_account'] = isset($v['default_account']) ? (string) $v['default_account'] : 'default';
+                    $v['accounts'] = array($v['default_account'] => $account);
+
+                    return $v;
+                })
+            ->end()
+            ->children()
+                ->scalarNode('default_account')->cannotBeEmpty()->defaultValue('default')->end()
+            ->end()
+            ->fixXmlConfig('account')
+            ->children()
+                ->arrayNode('accounts')
+                    ->isRequired()
+                    ->requiresAtLeastOneElement()
+                    ->useAttributeAsKey('name')
+                    ->prototype('array')
+                        ->validate()
+                            ->always(
+                                function ($v) {
+                                    $required = array();
+
+                                    switch ($v['type']) {
+                                        case 'web':
+                                            $required = array('oauth2_client_secret', 'oauth2_redirect_uri', 'developer_key', 'site_name');
+                                            break;
+
+                                        case 'service':
+                                            if ((isset($v['getenv']) && true === $v['getenv']) || isset($v['json_file']) || isset($v['access_token'])) {
+                                                return $v;
+                                            }
+
+                                            $required = array('oauth2_client_email', 'oauth2_private_key', 'oauth2_scopes');
+                                            break;
+                                    }
+
+                                    foreach ($required as $key) {
+                                        if (!isset($v[$key]) || empty($v[$key])) {
+                                            throw new \InvalidArgumentException(sprintf('"%s" is not set or empty', $key));
+                                        }
+                                    }
+
+                                    return $v;
+                                }
+                            )
+                        ->end()
+                        ->children()
+                            ->enumNode('type')->values(array('web', 'service'))->cannotBeEmpty()->defaultValue('web')->end()
+                            ->scalarNode('application_name')->isRequired()->cannotBeEmpty()->end()
+                            ->scalarNode('oauth2_client_id')->isRequired()->cannotBeEmpty()->end()
+                            ->scalarNode('oauth2_client_secret')->end()
+                            ->scalarNode('oauth2_client_email')->end()
+                            ->variableNode('access_token')->end()
+                            ->scalarNode('oauth2_private_key')->end()
+                            ->scalarNode('oauth2_redirect_uri')->end()
+                            ->variableNode('oauth2_scopes')->end()
+                            ->scalarNode('developer_key')->end()
+                            ->scalarNode('site_name')->end()
+                            ->scalarNode('getenv')->end()
+                            ->scalarNode('json_file')->end()
+
+                            ->scalarNode('authClass')->end()
+                            ->scalarNode('ioClass')->end()
+                            ->scalarNode('cacheClass')->end()
+                            ->scalarNode('basePath')->end()
+                            ->scalarNode('ioFileCache_directory')->end()
+                        ->end()
+                    ->end()
+                ->end()
+            ->end()
+        ;
+    }
 }
diff --git a/DependencyInjection/HappyRGoogleApiExtension.php b/DependencyInjection/HappyRGoogleApiExtension.php
index ec78141..6408fb3 100644
--- a/DependencyInjection/HappyRGoogleApiExtension.php
+++ b/DependencyInjection/HappyRGoogleApiExtension.php
@@ -3,28 +3,72 @@
 namespace HappyR\Google\ApiBundle\DependencyInjection;
 
 use Symfony\Component\DependencyInjection\ContainerBuilder;
-use Symfony\Component\Config\FileLocator;
-use Symfony\Component\HttpKernel\DependencyInjection\Extension;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\Reference;
+use Symfony\Component\HttpKernel\DependencyInjection\ConfigurableExtension;
 use Symfony\Component\DependencyInjection\Loader;
 
-/**
- * This is the class that loads and manages your bundle configuration
- *
- * To learn more see {@link http://symfony.com/doc/current/cookbook/bundles/extension.html}
- */
-class HappyRGoogleApiExtension extends Extension
+class HappyRGoogleApiExtension extends ConfigurableExtension
 {
     /**
      * {@inheritDoc}
      */
-    public function load(array $configs, ContainerBuilder $container)
+    public function loadInternal(array $config, ContainerBuilder $container)
     {
-        $configuration = new Configuration();
-        $config = $this->processConfiguration($configuration, $configs);
+        foreach ($config['accounts'] as $name => $account) {
+            $this->loadAccount($name, $account, $container);
+        }
 
-        $container->setParameter('happy_r_google_api', $config);
+        // Backwards compatibility
+        $default = $config['default_account'];
+        $container->setParameter('happy_r_google_api', array_merge($config['accounts'][$default], $config));
+        $container->setAlias('happyr.google.api.client', sprintf('happyr.google.api.%s_client', $default));
+        $container->setAlias('happyr.google.api.analytics', sprintf('happyr.google.api.%s_analytics', $default));
+        $container->setAlias('happyr.google.api.youtube', sprintf('happyr.google.api.%s_youtube', $default));
+    }
+
+    /**
+     * Define services for each account configuration.
+     *
+     * @param string           $name      The account name
+     * @param array            $config    The account configuration
+     * @param ContainerBuilder $container The container builder
+     */
+    public function loadAccount($name, array $config, ContainerBuilder $container)
+    {
+        $clientId = sprintf('happyr.google.api.%s_client', $name);
+        $client   = new Definition(
+            'HappyR\Google\ApiBundle\Services\GoogleClient',
+            array($config, new Reference('logger', ContainerInterface::IGNORE_ON_INVALID_REFERENCE))
+        );
+
+        $client->addTag('monolog.logger', array('channel' => 'google_client'));
+
+        $container->setDefinition($clientId, $client);
+
+        $container->setDefinition(
+            sprintf('happyr.google.api.%s_analytics', $name),
+            new Definition(
+                'HappyR\Google\ApiBundle\Services\AnalyticsService',
+                array(new Reference($clientId))
+            )
+        );
+
+        $container->setDefinition(
+            sprintf('happyr.google.api.%s_youtube', $name),
+            new Definition(
+                'HappyR\Google\ApiBundle\Services\YoutubeService',
+                array(new Reference($clientId))
+            )
+        );
 
-        $loader = new Loader\YamlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
-        $loader->load('services.yml');
+        $container->setDefinition(
+            sprintf('happyr.google.api.%s_groups_migration', $name),
+            new Definition(
+                'HappyR\Google\ApiBundle\Services\GroupsMigrationService',
+                array(new Reference($clientId))
+            )
+        );
     }
 }
diff --git a/README.md b/README.md
index 30bb14d..2c4bc6a 100644
--- a/README.md
+++ b/README.md
@@ -60,5 +60,45 @@ happy_r_google_api:
   site_name: mysite.com
 ```
 
+#### Advanced configuration
+
+You can set up multiple accounts, including service accounts.
+
+``` yaml
+# app/config/config.yml
+happy_r_google_api:
+  accounts:
+  
+    # regular web authentication
+    default:
+      type: web
+      application_name: MySite
+      oauth2_client_id: 
+      oauth2_client_secret: 
+      oauth2_redirect_uri: 
+      developer_key: 
+      site_name: mysite.com
+      
+    # Credentials from GOOGLE_APPLICATION_CREDENTIALS environment variable (recommended)
+    service_env:
+      type: service
+      getenv: true
+
+    # Credentials from service-account.json
+    service_file:
+      type: service
+      json_file: /path/to/your/service-account.json
+
+    # with service credentials, example to access Google Analytics
+    service_account:
+      type: service
+      application_name: MySite
+      oauth2_client_id: 
+      oauth2_client_email: 
+      oauth2_private_key: 
+      oauth2_scopes: 
+        - https://www.googleapis.com/auth/analytics.readonly
+```
+
 
 [1]: https://github.com/google/google-api-php-client
diff --git a/Resources/config/services.yml b/Resources/config/services.yml
deleted file mode 100644
index b5d59ff..0000000
--- a/Resources/config/services.yml
+++ /dev/null
@@ -1,18 +0,0 @@
-services:
-    happyr.google.api.client:
-        class: HappyR\Google\ApiBundle\Services\GoogleClient
-        arguments: ["%happy_r_google_api%", "@?logger"]
-        tags:
-            - { name: monolog.logger, channel: google_client }
-
-    happyr.google.api.analytics:
-        class: HappyR\Google\ApiBundle\Services\AnalyticsService
-        arguments: ["@happyr.google.api.client"]
-    
-    happyr.google.api.youtube:
-        class: HappyR\Google\ApiBundle\Services\YoutubeService
-        arguments: ["@happyr.google.api.client"]
-
-    happyr.google.api.groups_migration:
-        class: HappyR\Google\ApiBundle\Services\GroupsMigrationService
-        arguments: ["@happyr.google.api.client"]
diff --git a/Services/GoogleClient.php b/Services/GoogleClient.php
index 066c91c..3905de4 100644
--- a/Services/GoogleClient.php
+++ b/Services/GoogleClient.php
@@ -36,13 +36,57 @@ public function __construct(array $config, LoggerInterface $symfonyLogger = null
             }
         }
 
-        $client -> setApplicationName($config['application_name']);
-        $client -> setClientId($config['oauth2_client_id']);
-        $client -> setClientSecret($config['oauth2_client_secret']);
-        $client -> setRedirectUri($config['oauth2_redirect_uri']);
-        $client -> setDeveloperKey($config['developer_key']);
+        $client->setApplicationName($config['application_name']);
+        $client->setClientId($config['oauth2_client_id']);
 
-        $this -> client = $client;
+        switch ($config['type']) {
+            case 'web':
+                $client->setClientSecret($config['oauth2_client_secret']);
+                $client->setRedirectUri($config['oauth2_redirect_uri']);
+                $client->setDeveloperKey($config['developer_key']);
+                break;
+
+            case 'service':
+                $client->setAccessType('offline');
+                $client->setClientSecret($config['oauth2_client_secret']);
+                $client->setRedirectUri($config['oauth2_redirect_uri']);
+
+                if (isset($config['oauth2_scopes'])) {
+                    $client->setScopes($config['oauth2_scopes']);
+                }
+
+                if (isset($config['getenv']) && true === $config['getenv']) {
+                    $client->useApplicationDefaultCredentials();
+
+                } else if (isset($config['json_file'])) {
+                    $client->setAuthConfigFile($config['json_file']);
+
+                } else if (isset($config['access_token'])) {
+                    $client->setAccessToken($config['access_token']);
+
+                } else if (class_exists('\Google_Auth_AssertionCredentials')) {
+                    //BC for Google API 1.0
+                    $client->setAssertionCredentials(
+                        new \Google_Auth_AssertionCredentials(
+                            $config['oauth2_client_email'],
+                            $config['oauth2_scopes'],
+                            $config['oauth2_private_key']
+                        )
+                    );
+                } else {
+                    $client->setAuthConfig(
+                        array(
+                            'type'         => 'service_account',
+                            'client_id'    => $config['oauth2_client_id'],
+                            'client_email' => $config['oauth2_client_email'],
+                            'private_key'  => $config['oauth2_private_key'],
+                        )
+                    );
+                }
+                break;
+        }
+
+        $this->client = $client;
     }
 
     /**
diff --git a/composer.json b/composer.json
index e5b809f..9f5ecff 100644
--- a/composer.json
+++ b/composer.json
@@ -13,8 +13,8 @@
     ],
     "require": {
         "php": ">=5.3.2",
-        "symfony/framework-bundle": "2.*|~3.0",
-        "symfony/yaml": "2.*|~3.0",
+        "symfony/framework-bundle": "2.*|~3.0|^4.0|^5.0|^6.0",
+        "symfony/yaml": "2.*|~3.0|^4.0|^5.0|^6.0",
         "google/apiclient": "1.*|2.*"
     },
     "require-dev": {