diff --git a/src/Squidex.Infrastructure/StringExtensions.cs b/src/Squidex.Infrastructure/StringExtensions.cs
index 8808b649a..93a56333e 100644
--- a/src/Squidex.Infrastructure/StringExtensions.cs
+++ b/src/Squidex.Infrastructure/StringExtensions.cs
@@ -382,5 +382,20 @@ namespace Squidex.Infrastructure
 
             return result.ToString().Trim(separator);
         }
+
+        public static string BuildFullUrl(this string baseUrl, string path, bool trailingSlash = false)
+        {
+            var url = $"{baseUrl.TrimEnd('/')}/{path.Trim('/')}";
+
+            if (trailingSlash &&
+                url.IndexOf("#", StringComparison.OrdinalIgnoreCase) < 0 &&
+                url.IndexOf("?", StringComparison.OrdinalIgnoreCase) < 0 &&
+                url.IndexOf(";", StringComparison.OrdinalIgnoreCase) < 0)
+            {
+                url = url + "/";
+            }
+
+            return url;
+        }
     }
 }
diff --git a/src/Squidex/Config/Identity/IdentityUsage.cs b/src/Squidex/Config/Identity/IdentityUsage.cs
index 1838bf848..f08cbb6f4 100644
--- a/src/Squidex/Config/Identity/IdentityUsage.cs
+++ b/src/Squidex/Config/Identity/IdentityUsage.cs
@@ -14,6 +14,7 @@ using Microsoft.AspNetCore.Identity;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 using Squidex.Domain.Users;
+using Squidex.Infrastructure;
 using Squidex.Infrastructure.Log;
 using Squidex.Shared.Identity;
 using Squidex.Shared.Users;
@@ -93,10 +94,19 @@ namespace Squidex.Config.Identity
 
             if (!string.IsNullOrWhiteSpace(urlsOptions.BaseUrl))
             {
-                var apiAuthorityUrl = urlsOptions.BuildUrl(Constants.IdentityPrefix);
-
                 var identityOptions = app.ApplicationServices.GetService<IOptions<MyIdentityOptions>>().Value;
 
+                string apiAuthorityUrl;
+
+                if (!string.IsNullOrWhiteSpace(identityOptions.AuthorityUrl))
+                {
+                    apiAuthorityUrl = identityOptions.AuthorityUrl.BuildFullUrl(Constants.IdentityPrefix);
+                }
+                else
+                {
+                    apiAuthorityUrl = urlsOptions.BuildUrl(Constants.IdentityPrefix);
+                }
+
                 app.UseIdentityServerAuthentication(new IdentityServerAuthenticationOptions
                 {
                     Authority = apiAuthorityUrl,
diff --git a/src/Squidex/Config/Identity/MyIdentityOptions.cs b/src/Squidex/Config/Identity/MyIdentityOptions.cs
index 9dde059cb..ae8383df3 100644
--- a/src/Squidex/Config/Identity/MyIdentityOptions.cs
+++ b/src/Squidex/Config/Identity/MyIdentityOptions.cs
@@ -26,6 +26,8 @@ namespace Squidex.Config.Identity
 
         public string MicrosoftSecret { get; set; }
 
+        public string AuthorityUrl { get; set; }
+
         public bool RequiresHttps { get; set; }
 
         public bool AllowPasswordAuth { get; set; }
diff --git a/src/Squidex/Config/MyUrlsOptions.cs b/src/Squidex/Config/MyUrlsOptions.cs
index 19b462f3c..efcecc243 100644
--- a/src/Squidex/Config/MyUrlsOptions.cs
+++ b/src/Squidex/Config/MyUrlsOptions.cs
@@ -6,7 +6,6 @@
 //  All rights reserved.
 // ==========================================================================
 
-using System;
 using Squidex.Infrastructure;
 
 namespace Squidex.Config
@@ -23,17 +22,8 @@ namespace Squidex.Config
             {
                 throw new ConfigurationException("Configure BaseUrl with 'urls:baseUrl'.");
             }
-
-            var url = $"{BaseUrl.TrimEnd('/')}/{path.Trim('/')}";
-
-            if (trailingSlash &&
-                url.IndexOf("?", StringComparison.OrdinalIgnoreCase) < 0 &&
-                url.IndexOf(";", StringComparison.OrdinalIgnoreCase) < 0)
-            {
-                url = url + "/";
-            }
-
-            return url;
+            
+            return BaseUrl.BuildFullUrl(path, trailingSlash);
         }
     }
 }
diff --git a/tests/Squidex.Infrastructure.Tests/StringExtensionsTests.cs b/tests/Squidex.Infrastructure.Tests/StringExtensionsTests.cs
index 76861ac81..6448da561 100644
--- a/tests/Squidex.Infrastructure.Tests/StringExtensionsTests.cs
+++ b/tests/Squidex.Infrastructure.Tests/StringExtensionsTests.cs
@@ -103,5 +103,27 @@ namespace Squidex.Infrastructure
 
             Assert.Equal(value, value.WithFallback("fallback"));
         }
+
+        [Theory]
+        [InlineData("http://squidex.io/base/",  "path/to/res", false, "http://squidex.io/base/path/to/res")]
+        [InlineData("http://squidex.io/base/",  "path/to/res", true,  "http://squidex.io/base/path/to/res/")]
+        [InlineData("http://squidex.io/base/", "/path/to/res", true,  "http://squidex.io/base/path/to/res/")]
+        public void Should_provide_full_url_without_query_or_fragment(string baseUrl, string path, bool trailingSlash, string output)
+        {
+            var result = baseUrl.BuildFullUrl(path, trailingSlash);
+
+            Assert.Equal(output, result);
+        }
+
+        [Theory]
+        [InlineData("http://squidex.io/base/", "path/to/res?query=1", false, "http://squidex.io/base/path/to/res?query=1")]
+        [InlineData("http://squidex.io/base/", "path/to/res#query=1", true,  "http://squidex.io/base/path/to/res#query=1")]
+        [InlineData("http://squidex.io/base/", "path/to/res;query=1", true,  "http://squidex.io/base/path/to/res;query=1")]
+        public void Should_provide_full_url_wit_query_or_fragment(string baseUrl, string path, bool trailingSlash, string output)
+        {
+            var result = baseUrl.BuildFullUrl(path, trailingSlash);
+
+            Assert.Equal(output, result);
+        }
     }
 }