diff --git a/docs/core/compatibility/6.0.md b/docs/core/compatibility/6.0.md
index 7c2bc258d088b..00eed5eb4a5ca 100644
--- a/docs/core/compatibility/6.0.md
+++ b/docs/core/compatibility/6.0.md
@@ -1,7 +1,7 @@
 ---
 title: Breaking changes in .NET 6
 description: Navigate to the breaking changes in .NET 6.
-ms.date: 04/07/2021
+ms.date: 04/21/2021
 no-loc: [Blazor]
 ---
 # Breaking changes in .NET 6
@@ -23,6 +23,7 @@ If you're migrating an app to .NET 6, the breaking changes listed here might aff
 - [Middleware: HTTPS Redirection Middleware throws exception on ambiguous HTTPS ports](aspnet-core/6.0/middleware-ambiguous-https-ports-exception.md)
 - [Razor: Compiler no longer produces a Views assembly](aspnet-core/6.0/razor-compiler-doesnt-produce-views-assembly.md)
 - [Razor: RazorEngine APIs marked obsolete](aspnet-core/6.0/razor-engine-apis-obsolete.md)
+- [SignalR: Java Client updated to RxJava3](aspnet-core/6.0/signalr-java-client-updated.md)
 
 ## Core .NET libraries
 
diff --git a/docs/core/compatibility/aspnet-core/6.0/signalr-java-client-updated.md b/docs/core/compatibility/aspnet-core/6.0/signalr-java-client-updated.md
new file mode 100644
index 0000000000000..0be6eb240a391
--- /dev/null
+++ b/docs/core/compatibility/aspnet-core/6.0/signalr-java-client-updated.md
@@ -0,0 +1,44 @@
+---
+title: "Breaking change: SignalR Java Client updated to RxJava3"
+description: "Learn about the breaking change in ASP.NET Core 6.0 where the SignalR Java Client was updated to RxJava3."
+ms.date: 04/21/2021
+---
+# SignalR: Java Client updated to RxJava3
+
+The SignalR Java Client is now RxJava3.
+
+## Version introduced
+
+ASP.NET Core 6.0 preview 4
+
+## Old behavior
+
+The RxJava package reference in the library was RxJava2.
+
+## New behavior
+
+The RxJava package reference in the library is now RxJava3. For information about what changed in RxJava, see [What's different in 3.0](https://github.com/ReactiveX/RxJava/wiki/What's-different-in-3.0).
+
+## Reason for change
+
+The previous dependency (RxJava2) is no longer maintained. Support for RxJava2 ended in February 2021.
+
+## Recommended action
+
+If you were using RxJava2 in your app or library, you might need to update to RxJava3. For more information, see [What's different in 3.0](https://github.com/ReactiveX/RxJava/wiki/What's-different-in-3.0).
+
+## Affected APIs
+
+None.
+
+<!--
+
+## Category
+
+ASP.NET Core
+
+## Affected APIs
+
+Not detectable via API analysis.
+
+-->
diff --git a/docs/core/compatibility/toc.yml b/docs/core/compatibility/toc.yml
index 63faae27e0c56..92f60caad1fde 100644
--- a/docs/core/compatibility/toc.yml
+++ b/docs/core/compatibility/toc.yml
@@ -45,6 +45,8 @@ items:
           href: aspnet-core/6.0/razor-compiler-doesnt-produce-views-assembly.md
         - name: "Razor: RazorEngine APIs marked obsolete"
           href: aspnet-core/6.0/razor-engine-apis-obsolete.md
+        - name: "SignalR: Java Client updated to RxJava3"
+          href: aspnet-core/6.0/signalr-java-client-updated.md
       - name: Core .NET libraries
         items:
         - name: Nullability annotation changes
@@ -357,6 +359,8 @@ items:
           href: aspnet-core/6.0/razor-compiler-doesnt-produce-views-assembly.md
         - name: "Razor: RazorEngine APIs marked obsolete"
           href: aspnet-core/6.0/razor-engine-apis-obsolete.md
+        - name: "SignalR: Java Client updated to RxJava3"
+          href: aspnet-core/6.0/signalr-java-client-updated.md
       - name: .NET 5
         items:
         - name: ASP.NET Core apps deserialize quoted numbers