diff --git a/README.md b/README.md
index 570b5ab..bea96dd 100644
--- a/README.md
+++ b/README.md
@@ -181,6 +181,24 @@ gatuna/
     └── PingTest.cs          # PING/PONG network test with stats
 ```
 
+## Versioning
+
+Both programs use `MAJOR.MINOR.PATCH` where:
+
+- **MAJOR** matches the wire protocol version. A v2.x program rejects any frame
+  with `version != 2`. No cross-major compatibility.
+- **MINOR** is the main change indicator for features and fixes within a major
+  version.
+- **PATCH** is reserved for bug fixes; generally unused.
+
+Current version: **2.0.0** (wire protocol v2).
+
+Check versions:
+```sh
+gatunad --version          # Rust server
+```
+The Windows client shows its version in the title bar and tray tooltip.
+
 ## License
 
 CC0 1.0 Universal. See [`LICENSE`](LICENSE).
diff --git a/gatuna-win/MainForm.cs b/gatuna-win/MainForm.cs
index 595d574..99a197b 100644
--- a/gatuna-win/MainForm.cs
+++ b/gatuna-win/MainForm.cs
@@ -17,7 +17,8 @@ public partial class MainForm : Form
 
     public MainForm()
     {
-        Text = "gatuna";
+        var ver = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version!;
+        Text = $"gatuna {ver.Major}.{ver.Minor}";
         Width = 520;
         Height = 420;
         FormBorderStyle = FormBorderStyle.FixedSingle;
diff --git a/gatuna-win/Program.cs b/gatuna-win/Program.cs
index 59acfcf..1b1ddb9 100644
--- a/gatuna-win/Program.cs
+++ b/gatuna-win/Program.cs
@@ -9,10 +9,12 @@ static class Program
 
         var form = new MainForm();
 
+        var ver = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version!;
+
         using var tray = new NotifyIcon
         {
             Icon = SystemIcons.GetStockIcon(StockIconId.NetworkConnect, 32),
-            Text = "gatuna",
+            Text = $"gatuna {ver.Major}.{ver.Minor}",
             Visible = true,
         };
 
diff --git a/gatuna-win/app.manifest b/gatuna-win/app.manifest
index ba80e1c..ecd2013 100644
--- a/gatuna-win/app.manifest
+++ b/gatuna-win/app.manifest
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
-  <assemblyIdentity version="0.1.0.0" name="gatuna" />
+  <assemblyIdentity version="2.0.0.0" name="gatuna" />
   <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
     <security>
       <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
diff --git a/gatuna-win/gatuna.csproj b/gatuna-win/gatuna.csproj
index 4229f06..f92dc02 100644
--- a/gatuna-win/gatuna.csproj
+++ b/gatuna-win/gatuna.csproj
@@ -5,6 +5,7 @@
     <TargetFramework>net8.0-windows</TargetFramework>
     <AssemblyName>gatuna</AssemblyName>
     <RootNamespace>gatuna</RootNamespace>
+    <Version>2.0.0</Version>
     <Nullable>enable</Nullable>
     <UseWindowsForms>true</UseWindowsForms>
     <ImplicitUsings>enable</ImplicitUsings>
diff --git a/gatunad/Cargo.toml b/gatunad/Cargo.toml
index 4de11b8..a4e2756 100644
--- a/gatunad/Cargo.toml
+++ b/gatunad/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "gatuna"
-version = "0.1.0"
+version = "2.0.0"
 edition = "2021"
 license = "CC0-1.0"