diff --git a/Build/MQTTnet.nuspec b/Build/MQTTnet.nuspec
index c15d5321..42042a0e 100644
--- a/Build/MQTTnet.nuspec
+++ b/Build/MQTTnet.nuspec
@@ -12,7 +12,7 @@
     <requireLicenseAcceptance>true</requireLicenseAcceptance>
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</description>
     <releaseNotes>
-* [Server] ..
+* [Core] Added support for TLS 1.3 (requires .NET Core 3.1+) (thanks to @Dvergatal).
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2020</copyright>
     <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin Blazor</tags> 
diff --git a/Source/MQTTnet.Extensions.WebSocket4Net/WebSocket4NetMqttChannel.cs b/Source/MQTTnet.Extensions.WebSocket4Net/WebSocket4NetMqttChannel.cs
index 47d96821..120e6c36 100644
--- a/Source/MQTTnet.Extensions.WebSocket4Net/WebSocket4NetMqttChannel.cs
+++ b/Source/MQTTnet.Extensions.WebSocket4Net/WebSocket4NetMqttChannel.cs
@@ -16,14 +16,14 @@ using WebSocket4Net;
 
 namespace MQTTnet.Extensions.WebSocket4Net
 {
-    public class WebSocket4NetMqttChannel : IMqttChannel
+    public sealed class WebSocket4NetMqttChannel : IMqttChannel
     {
-        private readonly BlockingCollection<byte> _receiveBuffer = new BlockingCollection<byte>();
+        readonly BlockingCollection<byte> _receiveBuffer = new BlockingCollection<byte>();
 
-        private readonly IMqttClientOptions _clientOptions;
-        private readonly MqttClientWebSocketOptions _webSocketOptions;
+        readonly IMqttClientOptions _clientOptions;
+        readonly MqttClientWebSocketOptions _webSocketOptions;
 
-        private WebSocket _webSocket;
+        WebSocket _webSocket;
 
         public WebSocket4NetMqttChannel(IMqttClientOptions clientOptions, MqttClientWebSocketOptions webSocketOptions)
         {
@@ -166,12 +166,12 @@ namespace MQTTnet.Extensions.WebSocket4Net
             _webSocket = null;
         }
 
-        private void OnError(object sender, ErrorEventArgs e)
+        static void OnError(object sender, ErrorEventArgs e)
         {
             System.Diagnostics.Debug.Write(e.Exception.ToString());
         }
 
-        private void OnDataReceived(object sender, DataReceivedEventArgs e)
+        void OnDataReceived(object sender, DataReceivedEventArgs e)
         {
             foreach (var @byte in e.Data)
             {
@@ -179,7 +179,7 @@ namespace MQTTnet.Extensions.WebSocket4Net
             }
         }
 
-        private async Task ConnectInternalAsync(CancellationToken cancellationToken)
+        async Task ConnectInternalAsync(CancellationToken cancellationToken)
         {
             _webSocket.Error += OnError;
             _webSocket.DataReceived += OnDataReceived;
diff --git a/Source/MQTTnet.Server/Mqtt/MqttServerService.cs b/Source/MQTTnet.Server/Mqtt/MqttServerService.cs
index ac11aa44..bdb57624 100644
--- a/Source/MQTTnet.Server/Mqtt/MqttServerService.cs
+++ b/Source/MQTTnet.Server/Mqtt/MqttServerService.cs
@@ -212,7 +212,7 @@ namespace MQTTnet.Server.Mqtt
             // Configure encrypted connections
             if (_settings.EncryptedTcpEndPoint.Enabled)
             {
-#if NETCOREAPP3_0 || NET5_0
+#if NETCOREAPP3_1 || NET5_0
                 options
                     .WithEncryptedEndpoint()
                     .WithEncryptionSslProtocol(SslProtocols.Tls13);
diff --git a/Source/MQTTnet/Client/Options/MqttClientOptionsBuilderTlsParameters.cs b/Source/MQTTnet/Client/Options/MqttClientOptionsBuilderTlsParameters.cs
index 8f6abcc8..f73ab3b7 100644
--- a/Source/MQTTnet/Client/Options/MqttClientOptionsBuilderTlsParameters.cs
+++ b/Source/MQTTnet/Client/Options/MqttClientOptionsBuilderTlsParameters.cs
@@ -19,7 +19,7 @@ namespace MQTTnet.Client.Options
 
         public Func<MqttClientCertificateValidationCallbackContext, bool> CertificateValidationHandler { get; set; }
 
-#if NETCOREAPP3_0 || NET5_0
+#if NETCOREAPP3_1 || NET5_0
         public SslProtocols SslProtocol { get; set; } = SslProtocols.Tls13;
 #else
         public SslProtocols SslProtocol { get; set; } = SslProtocols.Tls12;
diff --git a/Source/MQTTnet/Client/Options/MqttClientTlsOptions.cs b/Source/MQTTnet/Client/Options/MqttClientTlsOptions.cs
index da926abd..b5e2c261 100644
--- a/Source/MQTTnet/Client/Options/MqttClientTlsOptions.cs
+++ b/Source/MQTTnet/Client/Options/MqttClientTlsOptions.cs
@@ -26,7 +26,7 @@ namespace MQTTnet.Client.Options
         public List<SslApplicationProtocol> ApplicationProtocols { get; set; }
 #endif
 
-#if NETCOREAPP3_0 || NET5_0
+#if NETCOREAPP3_1 || NET5_0
         public SslProtocols SslProtocol { get; set; } = SslProtocols.Tls13;
 #else
         public SslProtocols SslProtocol { get; set; } = SslProtocols.Tls12;
diff --git a/Source/MQTTnet/Implementations/MqttTcpChannel.Uwp.cs b/Source/MQTTnet/Implementations/MqttTcpChannel.Uwp.cs
index 20b798df..7d5706dd 100644
--- a/Source/MQTTnet/Implementations/MqttTcpChannel.Uwp.cs
+++ b/Source/MQTTnet/Implementations/MqttTcpChannel.Uwp.cs
@@ -39,11 +39,7 @@ namespace MQTTnet.Implementations
 
             CreateStreams();
 
-#if NETCOREAPP3_0 || NET5_0
-            IsSecureConnection = socket.Information.ProtectionLevel >= SocketProtectionLevel.Tls13;
-#else
             IsSecureConnection = socket.Information.ProtectionLevel >= SocketProtectionLevel.Tls12;
-#endif
             ClientCertificate = clientCertificate;
 
             Endpoint = _socket.Information.RemoteAddress + ":" + _socket.Information.RemotePort;
@@ -79,7 +75,7 @@ namespace MQTTnet.Implementations
                     _socket.Control.IgnorableServerCertificateErrors.Add(ignorableChainValidationResult);
                 }
 
-#if NETCOREAPP3_0 || NET5_0
+#if NETCOREAPP3_1 || NET5_0
                 var socketProtectionLevel = SocketProtectionLevel.Tls13;
                 if (_options.TlsOptions.SslProtocol == SslProtocols.Tls12)
                 {
@@ -89,7 +85,7 @@ namespace MQTTnet.Implementations
                 {
                     socketProtectionLevel = SocketProtectionLevel.Tls11;
                 }
-#else                
+#else
                 var socketProtectionLevel = SocketProtectionLevel.Tls12;
                 if (_options.TlsOptions.SslProtocol == SslProtocols.Tls11)
                 {