diff --git a/mod/contactgroup.php b/mod/contactgroup.php
deleted file mode 100644
index 07997cd11..000000000
--- a/mod/contactgroup.php
+++ /dev/null
@@ -1,53 +0,0 @@
-<?php
-
-use Friendica\App;
-use Friendica\Database\DBA;
-use Friendica\Model\Contact;
-use Friendica\Model\Group;
-
-function contactgroup_content(App $a)
-{
-	if (!local_user()) {
-		exit();
-	}
-
-	$change = null;
-	if (($a->argc > 2) && intval($a->argv[1]) && intval($a->argv[2])) {
-		$r = q("SELECT `id` FROM `contact` WHERE `id` = %d AND `uid` = %d and `self` = 0 and `blocked` = 0 AND `pending` = 0 LIMIT 1",
-			intval($a->argv[2]),
-			intval(local_user())
-		);
-		if (DBA::isResult($r)) {
-			$change = intval($a->argv[2]);
-		}
-	}
-
-	if (($a->argc > 1) && (intval($a->argv[1]))) {
-		$r = q("SELECT * FROM `group` WHERE `id` = %d AND `uid` = %d AND `deleted` = 0 LIMIT 1",
-			intval($a->argv[1]),
-			intval(local_user())
-		);
-		if (!DBA::isResult($r)) {
-			exit();
-		}
-
-		$group = $r[0];
-		$members = Contact::getByGroupId($group['id']);
-		$preselected = [];
-		if (count($members)) {
-			foreach ($members as $member) {
-				$preselected[] = $member['id'];
-			}
-		}
-
-		if (!empty($change)) {
-			if (in_array($change, $preselected)) {
-				Group::removeMember($group['id'], $change);
-			} else {
-				Group::addMember($group['id'], $change);
-			}
-		}
-	}
-
-	exit();
-}
diff --git a/mod/group.php b/mod/group.php
deleted file mode 100644
index a6f649bf3..000000000
--- a/mod/group.php
+++ /dev/null
@@ -1,313 +0,0 @@
-<?php
-/**
- * @file mod/group.php
- * @brief The group module (create and rename contact groups, add and
- *	remove contacts to the contact groups
- */
-
-use Friendica\App;
-use Friendica\BaseModule;
-use Friendica\Core\Config;
-use Friendica\Core\L10n;
-use Friendica\Core\PConfig;
-use Friendica\Core\Renderer;
-use Friendica\Database\DBA;
-use Friendica\Model;
-use Friendica\Module;
-use Friendica\Util\Strings;
-
-function group_init(App $a) {
-	if (local_user()) {
-		$a->page['aside'] = Model\Group::sidebarWidget('contact', 'group', 'extended', (($a->argc > 1) ? $a->argv[1] : 'everyone'));
-	}
-}
-
-function group_post(App $a) {
-
-	if (!local_user()) {
-		notice(L10n::t('Permission denied.') . EOL);
-		return;
-	}
-
-	if (($a->argc == 2) && ($a->argv[1] === 'new')) {
-		BaseModule::checkFormSecurityTokenRedirectOnError('/group/new', 'group_edit');
-
-		$name = Strings::escapeTags(trim($_POST['groupname']));
-		$r = Model\Group::create(local_user(), $name);
-		if ($r) {
-			info(L10n::t('Group created.') . EOL);
-			$r = Model\Group::getIdByName(local_user(), $name);
-			if ($r) {
-				$a->internalRedirect('group/' . $r);
-			}
-		} else {
-			notice(L10n::t('Could not create group.') . EOL);
-		}
-		$a->internalRedirect('group');
-		return; // NOTREACHED
-	}
-
-	if (($a->argc == 2) && intval($a->argv[1])) {
-		BaseModule::checkFormSecurityTokenRedirectOnError('/group', 'group_edit');
-
-		$r = q("SELECT * FROM `group` WHERE `id` = %d AND `uid` = %d LIMIT 1",
-			intval($a->argv[1]),
-			intval(local_user())
-		);
-		if (!DBA::isResult($r)) {
-			notice(L10n::t('Group not found.') . EOL);
-			$a->internalRedirect('contact');
-			return; // NOTREACHED
-		}
-		$group = $r[0];
-		$groupname = Strings::escapeTags(trim($_POST['groupname']));
-		if (strlen($groupname) && ($groupname != $group['name'])) {
-			$r = q("UPDATE `group` SET `name` = '%s' WHERE `uid` = %d AND `id` = %d",
-				DBA::escape($groupname),
-				intval(local_user()),
-				intval($group['id'])
-			);
-
-			if ($r) {
-				info(L10n::t('Group name changed.') . EOL);
-			}
-		}
-
-		$a->page['aside'] = Model\Group::sidebarWidget();
-	}
-	return;
-}
-
-function group_content(App $a) {
-	$change = false;
-
-	if (!local_user()) {
-		notice(L10n::t('Permission denied') . EOL);
-		return;
-	}
-
-	// With no group number provided we jump to the unassigned contacts as a starting point
-	if ($a->argc == 1) {
-		$a->internalRedirect('group/none');
-	}
-
-	// Switch to text mode interface if we have more than 'n' contacts or group members
-	$switchtotext = PConfig::get(local_user(), 'system', 'groupedit_image_limit');
-	if (is_null($switchtotext)) {
-		$switchtotext = Config::get('system', 'groupedit_image_limit', 400);
-	}
-
-	$tpl = Renderer::getMarkupTemplate('group_edit.tpl');
-
-	$context = [
-		'$submit' => L10n::t('Save Group'),
-		'$submit_filter' => L10n::t('Filter'),
-	];
-
-	if (($a->argc == 2) && ($a->argv[1] === 'new')) {
-		return Renderer::replaceMacros($tpl, $context + [
-			'$title' => L10n::t('Create a group of contacts/friends.'),
-			'$gname' => ['groupname', L10n::t('Group Name: '), '', ''],
-			'$gid' => 'new',
-			'$form_security_token' => BaseModule::getFormSecurityToken("group_edit"),
-		]);
-
-
-	}
-
-	$nogroup = false;
-
-	if (($a->argc == 2) && ($a->argv[1] === 'none')) {
-		$id = -1;
-		$nogroup = true;
-		$group = [
-			'id' => $id,
-			'name' => L10n::t('Contacts not in any group'),
-		];
-
-		$members = [];
-		$preselected = [];
-
-		$context = $context + [
-			'$title' => $group['name'],
-			'$gname' => ['groupname', L10n::t('Group Name: '), $group['name'], ''],
-			'$gid' => $id,
-			'$editable' => 0,
-		];
-	}
-
-
-	if (($a->argc == 3) && ($a->argv[1] === 'drop')) {
-		BaseModule::checkFormSecurityTokenRedirectOnError('/group', 'group_drop', 't');
-
-		if (intval($a->argv[2])) {
-			$r = q("SELECT `name` FROM `group` WHERE `id` = %d AND `uid` = %d LIMIT 1",
-				intval($a->argv[2]),
-				intval(local_user())
-			);
-
-			$result = null;
-
-			if (DBA::isResult($r)) {
-				$result = Model\Group::removeByName(local_user(), $r[0]['name']);
-			}
-
-			if ($result) {
-				info(L10n::t('Group removed.') . EOL);
-			} else {
-				notice(L10n::t('Unable to remove group.') . EOL);
-			}
-		}
-		$a->internalRedirect('group');
-		// NOTREACHED
-	}
-
-	if (($a->argc > 2) && intval($a->argv[1]) && intval($a->argv[2])) {
-		BaseModule::checkFormSecurityTokenForbiddenOnError('group_member_change', 't');
-
-		$r = q("SELECT `id` FROM `contact` WHERE `id` = %d AND `uid` = %d and `self` = 0 and `blocked` = 0 AND `pending` = 0 LIMIT 1",
-			intval($a->argv[2]),
-			intval(local_user())
-		);
-		if (DBA::isResult($r)) {
-			$change = intval($a->argv[2]);
-		}
-	}
-
-	if (($a->argc > 1) && intval($a->argv[1])) {
-		$r = q("SELECT * FROM `group` WHERE `id` = %d AND `uid` = %d AND `deleted` = 0 LIMIT 1",
-			intval($a->argv[1]),
-			intval(local_user())
-		);
-
-		if (!DBA::isResult($r)) {
-			notice(L10n::t('Group not found.') . EOL);
-			$a->internalRedirect('contact');
-		}
-
-		$group = $r[0];
-		$members = Model\Contact::getByGroupId($group['id']);
-		$preselected = [];
-
-		if (count($members)) {
-			foreach ($members as $member) {
-				$preselected[] = $member['id'];
-			}
-		}
-
-		if ($change) {
-			if (in_array($change, $preselected)) {
-				Model\Group::removeMember($group['id'], $change);
-			} else {
-				Model\Group::addMember($group['id'], $change);
-			}
-
-			$members = Model\Contact::getByGroupId($group['id']);
-			$preselected = [];
-			if (count($members)) {
-				foreach ($members as $member) {
-					$preselected[] = $member['id'];
-				}
-			}
-		}
-
-		$drop_tpl = Renderer::getMarkupTemplate('group_drop.tpl');
-		$drop_txt = Renderer::replaceMacros($drop_tpl, [
-			'$id' => $group['id'],
-			'$delete' => L10n::t('Delete Group'),
-			'$form_security_token' => BaseModule::getFormSecurityToken("group_drop"),
-		]);
-
-
-		$context = $context + [
-			'$title' => $group['name'],
-			'$gname' => ['groupname', L10n::t('Group Name: '), $group['name'], ''],
-			'$gid' => $group['id'],
-			'$drop' => $drop_txt,
-			'$form_security_token' => BaseModule::getFormSecurityToken('group_edit'),
-			'$edit_name' => L10n::t('Edit Group Name'),
-			'$editable' => 1,
-		];
-
-	}
-
-	if (!isset($group)) {
-		return;
-	}
-
-	$groupeditor = [
-		'label_members' => L10n::t('Members'),
-		'members' => [],
-		'label_contacts' => L10n::t('All Contacts'),
-		'group_is_empty' => L10n::t('Group is empty'),
-		'contacts' => [],
-	];
-
-	$sec_token = addslashes(BaseModule::getFormSecurityToken('group_member_change'));
-
-	// Format the data of the group members
-	foreach ($members as $member) {
-		if ($member['url']) {
-			$entry = Module\Contact::getContactTemplateVars($member);
-			$entry['label'] = 'members';
-			$entry['photo_menu'] = '';
-			$entry['change_member'] = [
-				'title'     => L10n::t("Remove contact from group"),
-				'gid'       => $group['id'],
-				'cid'       => $member['id'],
-				'sec_token' => $sec_token
-			];
-
-			$groupeditor['members'][] = $entry;
-		} else {
-			Model\Group::removeMember($group['id'], $member['id']);
-		}
-	}
-
-	if ($nogroup) {
-		$r = Model\Contact::getUngroupedList(local_user());
-	} else {
-		$r = q("SELECT * FROM `contact` WHERE `uid` = %d AND NOT `blocked` AND NOT `pending` AND NOT `self` ORDER BY `name` ASC",
-			intval(local_user())
-		);
-		$context['$desc'] = L10n::t('Click on a contact to add or remove.');
-	}
-
-	if (DBA::isResult($r)) {
-		// Format the data of the contacts who aren't in the contact group
-		foreach ($r as $member) {
-			if (!in_array($member['id'], $preselected)) {
-				$entry = Module\Contact::getContactTemplateVars($member);
-				$entry['label'] = 'contacts';
-				if (!$nogroup)
-					$entry['photo_menu'] = [];
-
-				if (!$nogroup) {
-					$entry['change_member'] = [
-						'title'     => L10n::t("Add contact to group"),
-						'gid'       => $group['id'],
-						'cid'       => $member['id'],
-						'sec_token' => $sec_token
-					];
-				}
-
-				$groupeditor['contacts'][] = $entry;
-			}
-		}
-	}
-
-	$context['$groupeditor'] = $groupeditor;
-
-	// If there are to many contacts we could provide an alternative view mode
-	$total = count($groupeditor['members']) + count($groupeditor['contacts']);
-	$context['$shortmode'] = (($switchtotext && ($total > $switchtotext)) ? true : false);
-
-	if ($change) {
-		$tpl = Renderer::getMarkupTemplate('groupeditor.tpl');
-		echo Renderer::replaceMacros($tpl, $context);
-		exit();
-	}
-
-	return Renderer::replaceMacros($tpl, $context);
-
-}
diff --git a/src/Core/System.php b/src/Core/System.php
index 69d15a176..45a88fe09 100644
--- a/src/Core/System.php
+++ b/src/Core/System.php
@@ -176,6 +176,12 @@ class System extends BaseObject
 		exit();
 	}
 
+	public static function jsonError($httpCode, $data, $content_type = 'application/json')
+	{
+		header($_SERVER["SERVER_PROTOCOL"] . ' ' . $httpCode);
+		self::jsonExit($data, $content_type);
+	}
+
 	/**
 	 * @brief Encodes content to json.
 	 *
diff --git a/src/Model/Contact.php b/src/Model/Contact.php
index d38d1cc10..bf7d806db 100644
--- a/src/Model/Contact.php
+++ b/src/Model/Contact.php
@@ -232,6 +232,11 @@ class Contact extends BaseObject
 		}
 
 		DBA::update('user-contact', ['blocked' => $blocked], ['cid' => $cdata['public'], 'uid' => $uid], true);
+
+		if ($blocked) {
+			// Blocked contact can't be in any group
+			self::removeFromGroups($cid);
+		}
 	}
 
 	/**
@@ -2220,4 +2225,9 @@ class Contact extends BaseObject
 
 		return $redirect;
 	}
+
+	public static function removeFromGroups($contact_id)
+	{
+		return DBA::delete('group_member', ['contact-id' => $contact_id]);
+	}
 }
diff --git a/src/Model/Group.php b/src/Model/Group.php
index 0af10995b..feff4661a 100644
--- a/src/Model/Group.php
+++ b/src/Model/Group.php
@@ -16,6 +16,26 @@ use Friendica\Database\DBA;
  */
 class Group extends BaseObject
 {
+	/**
+	 *
+	 *
+	 * @param int $group_id
+	 * @return bool
+	 * @throws \Exception
+	 */
+	public static function exists($group_id, $uid = null)
+	{
+		$condition = ['id' => $group_id, 'deleted' => false];
+
+		if (isset($uid)) {
+			$condition = [
+				'uid' => $uid
+			];
+		}
+
+		return DBA::exists('group', $condition);
+	}
+
 	/**
 	 * @brief Create a new contact group
 	 *
diff --git a/src/Module/Group.php b/src/Module/Group.php
new file mode 100644
index 000000000..747ec1e56
--- /dev/null
+++ b/src/Module/Group.php
@@ -0,0 +1,350 @@
+<?php
+/**
+ * @file src/Module/Group.php
+ */
+
+namespace Friendica\Module;
+
+use Friendica\BaseModule;
+use Friendica\Core\Config;
+use Friendica\Core\L10n;
+use Friendica\Core\PConfig;
+use Friendica\Core\Renderer;
+use Friendica\Core\System;
+use Friendica\Database\DBA;
+use Friendica\Model;
+use Friendica\Util\Strings;
+
+require_once 'boot.php';
+
+class Group extends BaseModule
+{
+	public static function post()
+	{
+		$a = self::getApp();
+
+		if ($a->isAjax()) {
+			self::ajaxPost();
+		}
+
+		if (!local_user()) {
+			notice(L10n::t('Permission denied.'));
+			$a->internalRedirect();
+		}
+
+		if (($a->argc == 2) && ($a->argv[1] === 'new')) {
+			BaseModule::checkFormSecurityTokenRedirectOnError('/group/new', 'group_edit');
+
+			$name = Strings::escapeTags(trim($_POST['groupname']));
+			$r = Model\Group::create(local_user(), $name);
+			if ($r) {
+				info(L10n::t('Group created.'));
+				$r = Model\Group::getIdByName(local_user(), $name);
+				if ($r) {
+					$a->internalRedirect('group/' . $r);
+				}
+			} else {
+				notice(L10n::t('Could not create group.'));
+			}
+			$a->internalRedirect('group');
+		}
+
+		if (($a->argc == 2) && intval($a->argv[1])) {
+			BaseModule::checkFormSecurityTokenRedirectOnError('/group', 'group_edit');
+
+			$group = DBA::selectFirst('group', ['id', 'name'], ['id' => $a->argv[1], 'uid' => local_user()]);
+			if (!DBA::isResult($group)) {
+				notice(L10n::t('Group not found.'));
+				$a->internalRedirect('contact');
+			}
+			$groupname = Strings::escapeTags(trim($_POST['groupname']));
+			if (strlen($groupname) && ($groupname != $group['name'])) {
+				if (Model\Group::update($group['id'], $groupname)) {
+					info(L10n::t('Group name changed.'));
+				}
+			}
+		}
+	}
+
+	public static function ajaxPost()
+	{
+		try {
+			$a = self::getApp();
+
+			if (!local_user()) {
+				throw new \Exception(L10n::t('Permission denied.'), 403);
+			}
+
+			// POST /group/123/add/123
+			// POST /group/123/remove/123
+			if ($a->argc == 4) {
+				list($group_id, $command, $contact_id) = array_slice($a->argv, 1);
+
+				if (!Model\Group::exists($group_id, local_user())) {
+					throw new \Exception(L10n::t('Unknown group.'), 404);
+				}
+
+				$contact = DBA::selectFirst('contact', ['pending', 'blocked', 'deleted'], ['id' => $contact_id, 'uid' => local_user()]);
+				if (!DBA::isResult($contact)) {
+					throw new \Exception(L10n::t('Contact not found.'), 404);
+				}
+
+				if ($contact['pending']) {
+					throw new \Exception(L10n::t('Contact is unavailable.'), 400);
+				}
+
+				if ($contact['deleted']) {
+					throw new \Exception(L10n::t('Contact is deleted.'), 410);
+				}
+
+				switch($command) {
+					case 'add':
+						if ($contact['blocked']) {
+							throw new \Exception(L10n::t('Contact is blocked, unable to add it to a group.'), 400);
+						}
+
+						if (!Model\Group::addMember($group_id, $contact_id)) {
+							throw new \Exception(L10n::t('Unable to add the contact to the group.'), 500);
+						}
+						$message = L10n::t('Contact successfully added to group.');
+						break;
+					case 'remove':
+						if (!Model\Group::removeMember($group_id, $contact_id)) {
+							throw new \Exception(L10n::t('Unable to remove the contact from the group.'), 500);
+						}
+						$message = L10n::t('Contact successfully removed from group.');
+						break;
+					default:
+						throw new \Exception(L10n::t('Unknown group command.'), 400);
+				}
+			} else {
+				throw new \Exception(L10n::t('Bad request.'), 400);
+			}
+
+			notice($message);
+			System::jsonExit(['status' => 'OK', 'message' => $message]);
+		} catch (\Exception $e) {
+			notice($e->getMessage());
+			System::jsonError($e->getCode(), ['status' => 'error', 'message' => $e->getMessage()]);
+		}
+	}
+
+	public static function content()
+	{
+		$change = false;
+
+		if (!local_user()) {
+			System::httpExit(403);
+		}
+
+		$a = self::getApp();
+
+		$a->page['aside'] = Model\Group::sidebarWidget('contact', 'group', 'extended', (($a->argc > 1) ? $a->argv[1] : 'everyone'));
+
+		// With no group number provided we jump to the unassigned contacts as a starting point
+		if ($a->argc == 1) {
+			$a->internalRedirect('group/none');
+		}
+
+		// Switch to text mode interface if we have more than 'n' contacts or group members
+		$switchtotext = PConfig::get(local_user(), 'system', 'groupedit_image_limit');
+		if (is_null($switchtotext)) {
+			$switchtotext = Config::get('system', 'groupedit_image_limit', 200);
+		}
+
+		$tpl = Renderer::getMarkupTemplate('group_edit.tpl');
+
+
+		$context = [
+			'$submit' => L10n::t('Save Group'),
+			'$submit_filter' => L10n::t('Filter'),
+		];
+
+		if (($a->argc == 2) && ($a->argv[1] === 'new')) {
+			return Renderer::replaceMacros($tpl, $context + [
+				'$title' => L10n::t('Create a group of contacts/friends.'),
+				'$gname' => ['groupname', L10n::t('Group Name: '), '', ''],
+				'$gid' => 'new',
+				'$form_security_token' => BaseModule::getFormSecurityToken("group_edit"),
+			]);
+		}
+
+		$nogroup = false;
+
+		if (($a->argc == 2) && ($a->argv[1] === 'none')) {
+			$id = -1;
+			$nogroup = true;
+			$group = [
+				'id' => $id,
+				'name' => L10n::t('Contacts not in any group'),
+			];
+
+			$members = [];
+			$preselected = [];
+
+			$context = $context + [
+				'$title' => $group['name'],
+				'$gname' => ['groupname', L10n::t('Group Name: '), $group['name'], ''],
+				'$gid' => $id,
+				'$editable' => 0,
+			];
+		}
+
+		if (($a->argc == 3) && ($a->argv[1] === 'drop')) {
+			BaseModule::checkFormSecurityTokenRedirectOnError('/group', 'group_drop', 't');
+
+			if (intval($a->argv[2])) {
+				if (!Model\Group::exists($a->argv[2], local_user())) {
+					notice(L10n::t('Group not found.'));
+					$a->internalRedirect('contact');
+				}
+
+				if (Model\Group::remove($a->argv[2])) {
+					info(L10n::t('Group removed.'));
+				} else {
+					notice(L10n::t('Unable to remove group.'));
+				}
+			}
+			$a->internalRedirect('group');
+		}
+
+		if (($a->argc > 2) && intval($a->argv[1]) && intval($a->argv[2])) {
+			BaseModule::checkFormSecurityTokenForbiddenOnError('group_member_change', 't');
+
+			if (DBA::exists('contact', ['id' => $a->argv[2], 'uid' => local_user(), 'self' => false, 'pending' => false, 'blocked' => false])) {
+				$change = intval($a->argv[2]);
+			}
+		}
+
+		if (($a->argc > 1) && intval($a->argv[1])) {
+			$group = DBA::selectFirst('group', ['id', 'name'], ['id' => $a->argv[1], 'uid' => local_user(), 'deleted' => false]);
+			if (!DBA::isResult($group)) {
+				notice(L10n::t('Group not found.'));
+				$a->internalRedirect('contact');
+			}
+
+			$members = Model\Contact::getByGroupId($group['id']);
+			$preselected = [];
+
+			if (count($members)) {
+				foreach ($members as $member) {
+					$preselected[] = $member['id'];
+				}
+			}
+
+			if ($change) {
+				if (in_array($change, $preselected)) {
+					Model\Group::removeMember($group['id'], $change);
+				} else {
+					Model\Group::addMember($group['id'], $change);
+				}
+
+				$members = Model\Contact::getByGroupId($group['id']);
+				$preselected = [];
+				if (count($members)) {
+					foreach ($members as $member) {
+						$preselected[] = $member['id'];
+					}
+				}
+			}
+
+			$drop_tpl = Renderer::getMarkupTemplate('group_drop.tpl');
+			$drop_txt = Renderer::replaceMacros($drop_tpl, [
+				'$id' => $group['id'],
+				'$delete' => L10n::t('Delete Group'),
+				'$form_security_token' => BaseModule::getFormSecurityToken("group_drop"),
+			]);
+
+			$context = $context + [
+				'$title' => $group['name'],
+				'$gname' => ['groupname', L10n::t('Group Name: '), $group['name'], ''],
+				'$gid' => $group['id'],
+				'$drop' => $drop_txt,
+				'$form_security_token' => BaseModule::getFormSecurityToken('group_edit'),
+				'$edit_name' => L10n::t('Edit Group Name'),
+				'$editable' => 1,
+			];
+		}
+
+		if (!isset($group)) {
+			System::httpExit(400);
+		}
+
+		$groupeditor = [
+			'label_members' => L10n::t('Members'),
+			'members' => [],
+			'label_contacts' => L10n::t('All Contacts'),
+			'group_is_empty' => L10n::t('Group is empty'),
+			'contacts' => [],
+		];
+
+		$sec_token = addslashes(BaseModule::getFormSecurityToken('group_member_change'));
+
+		// Format the data of the group members
+		foreach ($members as $member) {
+			if ($member['url']) {
+				$entry = Contact::getContactTemplateVars($member);
+				$entry['label'] = 'members';
+				$entry['photo_menu'] = '';
+				$entry['change_member'] = [
+					'title'     => L10n::t("Remove contact from group"),
+					'gid'       => $group['id'],
+					'cid'       => $member['id'],
+					'sec_token' => $sec_token
+				];
+
+				$groupeditor['members'][] = $entry;
+			} else {
+				Model\Group::removeMember($group['id'], $member['id']);
+			}
+		}
+
+		if ($nogroup) {
+			$contacts = Model\Contact::getUngroupedList(local_user());
+		} else {
+			$contacts_stmt = DBA::select('contact', [],
+				['uid' => local_user(), 'pending' => false, 'blocked' => false, 'self' => false],
+				['order' => ['name']]
+			);
+			$contacts = DBA::toArray($contacts_stmt);
+			$context['$desc'] = L10n::t('Click on a contact to add or remove.');
+		}
+
+		if (DBA::isResult($contacts)) {
+			// Format the data of the contacts who aren't in the contact group
+			foreach ($contacts as $member) {
+				if (!in_array($member['id'], $preselected)) {
+					$entry = Contact::getContactTemplateVars($member);
+					$entry['label'] = 'contacts';
+					if (!$nogroup)
+						$entry['photo_menu'] = [];
+
+					if (!$nogroup) {
+						$entry['change_member'] = [
+							'title'     => L10n::t("Add contact to group"),
+							'gid'       => $group['id'],
+							'cid'       => $member['id'],
+							'sec_token' => $sec_token
+						];
+					}
+
+					$groupeditor['contacts'][] = $entry;
+				}
+			}
+		}
+
+		$context['$groupeditor'] = $groupeditor;
+
+		// If there are to many contacts we could provide an alternative view mode
+		$total = count($groupeditor['members']) + count($groupeditor['contacts']);
+		$context['$shortmode'] = (($switchtotext && ($total > $switchtotext)) ? true : false);
+
+		if ($change) {
+			$tpl = Renderer::getMarkupTemplate('groupeditor.tpl');
+			echo Renderer::replaceMacros($tpl, $context);
+			exit();
+		}
+
+		return Renderer::replaceMacros($tpl, $context);
+	}
+}
\ No newline at end of file
diff --git a/view/js/main.js b/view/js/main.js
index 3370d7ccd..cd09de014 100644
--- a/view/js/main.js
+++ b/view/js/main.js
@@ -793,11 +793,25 @@ function profChangeMember(gid,cid) {
 	});
 }
 
-function contactgroupChangeMember(gid,cid) {
+function contactgroupChangeMember(checkbox, gid, cid) {
+	let url;
+	// checkbox.checked is the checkbox state after the click
+	if (checkbox.checked) {
+		url = 'group/' + gid + '/add/' + cid;
+	} else {
+		url = 'group/' + gid + '/remove/' + cid;
+	}
 	$('body').css('cursor', 'wait');
-	$.get('contactgroup/' + gid + '/' + cid, function(data) {
-			$('body').css('cursor', 'auto');
+	$.post(url)
+	.error(function () {
+		// Restores previous state in case of error
+		checkbox.checked = !checkbox.checked;
+	})
+	.always(function() {
+		$('body').css('cursor', 'auto');
 	});
+
+	return true;
 }
 
 function checkboxhighlight(box) {
diff --git a/view/templates/group_side.tpl b/view/templates/group_side.tpl
index 5796bb735..31b9287ba 100644
--- a/view/templates/group_side.tpl
+++ b/view/templates/group_side.tpl
@@ -9,7 +9,7 @@
 					{{if $group.cid}}
 						<input type="checkbox"
 							class="{{if $group.selected}}ticked{{else}}unticked {{/if}} action"
-							onclick="contactgroupChangeMember('{{$group.id}}','{{$group.cid}}');return true;"
+							onclick="return contactgroupChangeMember(this, '{{$group.id}}','{{$group.cid}}');"
 							{{if $group.ismember}}checked="checked"{{/if}}
 						/>
 					{{/if}}
diff --git a/view/theme/frio/templates/group_side.tpl b/view/theme/frio/templates/group_side.tpl
index 947ae974e..75983b36e 100644
--- a/view/theme/frio/templates/group_side.tpl
+++ b/view/theme/frio/templates/group_side.tpl
@@ -28,7 +28,7 @@
 							<input type="checkbox"
 								id="sidebar-group-checkbox-{{$group.id}}"
 								class="{{if $group.selected}}ticked{{else}}unticked {{/if}} action"
-								onclick="contactgroupChangeMember('{{$group.id}}','{{$group.cid}}');return true;"
+								onclick="return contactgroupChangeMember(this, '{{$group.id}}','{{$group.cid}}');"
 								{{if $group.ismember}}checked="checked"{{/if}}
 								aria-checked="{{if $group.ismember}}true{{else}}false{{/if}}"
 							/>
diff --git a/view/theme/quattro/templates/group_side.tpl b/view/theme/quattro/templates/group_side.tpl
index 620d2de75..18a6105a6 100644
--- a/view/theme/quattro/templates/group_side.tpl
+++ b/view/theme/quattro/templates/group_side.tpl
@@ -17,7 +17,7 @@
 				{{if $group.cid}}
 					<input type="checkbox"
 						class="{{if $group.selected}}ticked{{else}}unticked {{/if}} action"
-						onclick="contactgroupChangeMember('{{$group.id}}','{{$group.cid}}');return true;"
+						onclick="return contactgroupChangeMember(this, '{{$group.id}}','{{$group.cid}}');"
 						{{if $group.ismember}}checked="checked"{{/if}}
 					/>
 				{{/if}}