diff --git a/Microsoft.Azure.Cosmos/src/UserAgentContainer.cs b/Microsoft.Azure.Cosmos/src/UserAgentContainer.cs
index 4a7a7ddd91..54a04cc5ff 100644
--- a/Microsoft.Azure.Cosmos/src/UserAgentContainer.cs
+++ b/Microsoft.Azure.Cosmos/src/UserAgentContainer.cs
@@ -64,8 +64,11 @@ private string CreateBaseUserAgentString(
 
             // Regex replaces all special characters with empty space except . - | since they do not cause format exception for the user agent string.
             // Do not change the cosmos-netstandard-sdk as it is required for reporting
-            string baseUserAgent = $"cosmos-netstandard-sdk/{clientVersion}" + Regex.Replace($"|{directVersion}|{this.clientId}|{processArchitecture}|{operatingSystem}|{runtimeFramework}|", @"[^0-9a-zA-Z\.\|\-]+", " ");
-
+            string previewFlag = string.Empty;
+#if PREVIEW
+            previewFlag = "P";
+#endif
+            string baseUserAgent = $"cosmos-netstandard-sdk/{clientVersion}" + previewFlag + Regex.Replace($"|{directVersion}|{this.clientId}|{processArchitecture}|{operatingSystem}|{runtimeFramework}|", @"[^0-9a-zA-Z\.\|\-]+", " ");
             if (!string.IsNullOrEmpty(regionConfiguration))
             {
                 baseUserAgent += $"{regionConfiguration}|";
diff --git a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/UserAgentTests.cs b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/UserAgentTests.cs
index c0906969a5..4941e61f8a 100644
--- a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/UserAgentTests.cs
+++ b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/UserAgentTests.cs
@@ -88,7 +88,11 @@ public void VerifyUserAgentContent()
 
             Assert.IsTrue(serialization.Contains(envInfo.ProcessArchitecture));
             string[] values = serialization.Split('|');
-            Assert.AreEqual($"cosmos-netstandard-sdk/{envInfo.ClientVersion}", values[0]);
+            string previewFlag = string.Empty;
+#if PREVIEW
+            previewFlag = "P";
+#endif
+            Assert.AreEqual($"cosmos-netstandard-sdk/{envInfo.ClientVersion}" + previewFlag, values[0]);
             Assert.AreEqual(envInfo.DirectVersion, values[1]);
             Assert.AreEqual("0", values[2]);
             Assert.AreEqual(envInfo.ProcessArchitecture, values[3]);
@@ -100,7 +104,7 @@ public void VerifyUserAgentContent()
         public async Task VerifyUserAgentWithRegionConfiguration()
         {
             string databaseName = Guid.NewGuid().ToString();
-            string containerName = Guid.NewGuid().ToString();
+            string containerName = Guid.NewGuid().ToString();           
 
             {
                 CosmosClientOptions cosmosClientOptions = new CosmosClientOptions();