diff --git a/Classes/Client.php b/Classes/Client.php
index 83ceeeb..d55ebca 100644
--- a/Classes/Client.php
+++ b/Classes/Client.php
@@ -146,17 +146,69 @@ protected function checkAccess(ServerRequestInterface $request): string
             return 'No secret or too small secret defined';
         }
 
-        if (!isset($settings['allowedIps']) || empty($settings['allowedIps'])) {
-            return 'No allowed ips defined';
+        /* Only returns an error when both are empty */
+        if (empty($settings['allowedIps']) && empty($settings['allowedDomains'])) {
+            return 'No allowed ips or domains defined';
         }
+
+        $allowedIps = $this->getAllowedIps($settings['allowedIps'], $settings['allowedDomains']);
+
         $remoteIp = GeneralUtility::getIndpEnv('REMOTE_ADDR');
-        if (!GeneralUtility::cmpIP($remoteIp, $settings['allowedIps'])) {
+        if (!GeneralUtility::cmpIP($remoteIp, $allowedIps)) {
             return sprintf('IP comparison failed, remote IP: %s!', $remoteIp);
         }
 
         return '';
     }
 
+    /**
+     * Parses the allowed domains and IPs from the extension settings into a single allowed IPs string
+     * @return string The allowed ips, comma separated.
+     */
+    public function getAllowedIps(string $allowedIps, string $allowedDomains): string
+    {
+        $allowedIps = trim($allowedIps);
+        $allowedDomains = trim($allowedDomains);
+
+        /* Return * when anything is allowed in one field, and the other is empty */
+        if (($allowedIps === '*' && $allowedDomains === '*') ||
+            ($allowedIps === '*' && empty($allowedDomains)) ||
+            (empty($allowedIps) && $allowedDomains === '*')) {
+            return '*';
+        }
+
+        $allowedIpsResult = '';
+        if($allowedIps !== '*' && !empty($allowedIps)) {
+            $allowedIpsResult = sprintf('%s, ', $allowedIps);
+        }
+
+        /* Convert the domain names to IP addresses */
+        if($allowedDomains !== '*' && !empty($allowedDomains)) {
+            $allowedDomainsArray = explode(',', $allowedDomains);
+            foreach ($allowedDomainsArray as $allowedDomain) {
+                $resultsIpv4 = @dns_get_record($allowedDomain, DNS_A);
+                if($resultsIpv4) {
+                    foreach ($resultsIpv4 as $resultIpv4) {
+                        if(isset($resultIpv4['ip'])) {
+                            $allowedIpsResult .= sprintf('%s, ', $resultIpv4['ip']);
+                        }
+                    }
+                }
+                $resultsIpv6 = @dns_get_record($allowedDomain, DNS_AAAA);
+                if($resultsIpv6) {
+                    foreach ($resultsIpv6 as $resultIpv6) {
+                        if(isset($resultIpv6['ipv6'])) {
+                            $allowedIpsResult .= sprintf('%s, ', $resultIpv6['ipv6']);
+                        }
+                    }
+                }
+            }
+        }
+
+        /* Return concatenated IPs and domains IPs */
+        return trim($allowedIpsResult, ' ,');
+    }
+
     protected function getSettings(): array
     {
         $configuration = [];
diff --git a/README.rst b/README.rst
index 6dfa6a4..d6e302a 100644
--- a/README.rst
+++ b/README.rst
@@ -29,6 +29,10 @@ allowedIps
 """"""""""
 Define a comma separated list of IPs which are allowed to fetch the client data.
 
+allowedDomains
+""""""""""
+Define a comma separated list of domains which are allowed to fetch the client data.
+
 enableDebugForErrors
 """"""""""""""""""""
 If set, the errors are outputted if you call `http://yourdomain.tld/?eID=t3monitoring&secret=<yoursecret>`. This can help to identify problems.
diff --git a/Tests/Unit/ClientTest.php b/Tests/Unit/ClientTest.php
new file mode 100644
index 0000000..0c25243
--- /dev/null
+++ b/Tests/Unit/ClientTest.php
@@ -0,0 +1,148 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+use T3Monitor\T3monitoringClient\Client;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+
+class ClientTest extends TestCase
+{
+
+    /**
+     * @var Client
+     */
+    protected $client;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        /** @var Client $client */
+        $this->client = GeneralUtility::makeInstance(Client::class);
+    }
+
+    /**
+     * @test
+     */
+    public function testInputIpsAndDomainsStarsReturnOneStarOnly()
+    {
+        $allowedIps = '*';
+        $allowedDomains = '*';
+        $this->assertEquals('*', $this->client->getAllowedIps($allowedIps, $allowedDomains));
+
+        $allowedIps = '*';
+        $allowedDomains = '';
+        $this->assertEquals('*', $this->client->getAllowedIps($allowedIps, $allowedDomains));
+
+        $allowedIps = '';
+        $allowedDomains = '*';
+        $this->assertEquals('*', $this->client->getAllowedIps($allowedIps, $allowedDomains));
+    }
+
+    /**
+     * @test
+     */
+    public function testValuesHasPriorityOverStarOverEmpty()
+    {
+        $allowedIps = '78.47.171.202, 142.250.184.206';
+        $allowedDomains = '*';
+        /* Expect the IPs to be returned */
+        $this->assertCount(
+            2,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+
+        $allowedIps = '78.47.171.202, 142.250.184.206';
+        $allowedDomains = '';
+        /* Expect the IPs to be returned */
+        $this->assertCount(
+            2,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+
+        $allowedIps = '*';
+        $allowedDomains = 'www.google.com, www.test.io';
+        /* Expect the IPs from the domains to be returned */
+        $this->assertGreaterThanOrEqual(
+            2,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+
+        $allowedIps = '';
+        $allowedDomains = 'www.google.com, www.test.io';
+        /* Expect the IPs from the domains to be returned */
+        $this->assertGreaterThanOrEqual(
+            2,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function testInputDomainsOnlyReturnsIPv4AndIPv6()
+    {
+        $allowedIps = '';
+        $allowedDomains = 'www.google.com';
+
+        /* Expect the IPs to be returned */
+        $this->assertGreaterThanOrEqual(
+            1,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function testInputIpsAndDomainsReturnsBothConcatenated()
+    {
+        $allowedIps = '78.47.171.202, 142.250.184.206';
+        $allowedDomains = 'www.google.com, www.test.io';
+
+        /* Expect 4 or more IPs (depending on IPv6 implementation and ) to be returned */
+        $this->assertGreaterThanOrEqual(
+            4,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function testExpectTypeErrorOnNull()
+    {
+        $allowedIps = null;
+        $allowedDomains = null;
+
+        $this->expectException(TypeError::class);
+        $this->client->getAllowedIps($allowedIps, $allowedDomains);
+    }
+
+    /**
+     * @test
+     */
+    public function testExpectZeroIpsWithEmptyParameters()
+    {
+        $allowedIps = '';
+        $allowedDomains = '';
+
+        $this->assertEquals(
+            '',
+            $this->client->getAllowedIps($allowedIps, $allowedDomains)
+        );
+    }
+
+    /**
+     * @test
+     */
+    public function testExpectBogusDomainNamesToNotBeProcessed()
+    {
+        $allowedIps = '78.47.171.202, 142.250.184.206';
+        $allowedDomains = 'com.google.www, io.test.www, test@test.com, www,test,io, www/test/io, jksdafjsdnidmfhsnbsdfkjnjuhasghdsn.nl';
+
+        $this->assertCount(
+            2,
+            explode(',', $this->client->getAllowedIps($allowedIps, $allowedDomains))
+        );
+    }
+
+}
diff --git a/ext_conf_template.txt b/ext_conf_template.txt
index 7c34928..f96061c 100644
--- a/ext_conf_template.txt
+++ b/ext_conf_template.txt
@@ -6,4 +6,7 @@ secret =
 allowedIps = *
 
 # cat=features/enable/3; type=boolean; label=Enable debugging: Instead of silently stopping the endpoint call, the error is outputted. Just enable this to debug if a connection is not possible!
-enableDebugForErrors = 0
\ No newline at end of file
+enableDebugForErrors = 0
+
+# cat=features/enable/2; type=string; label=Allowed domains:Restrict the endpoint to specific domains. Comma separated lists are possible
+allowedDomains = *