diff --git a/packages/web/src/App.svelte b/packages/web/src/App.svelte
index 75b78a7..22ab213 100644
--- a/packages/web/src/App.svelte
+++ b/packages/web/src/App.svelte
@@ -1252,6 +1252,7 @@
   <header class="masthead">
     <span class="mast-title">Wiz-War</span>
     <span class="mast-sub">sixth edition</span>
+    <span class="mast-version" title="deployed">{__BUILD_STAMP__}</span>
     <button class="mast-leave" title="preferences" onclick={() => (prefsOpen = !prefsOpen)}>⚙ preferences</button>
     {#if local.active}
       <span class="mast-room">hotseat</span>
@@ -2448,6 +2449,12 @@
     text-transform: uppercase;
     color: #8d8672;
   }
+  .mast-version {
+    font-family: "Courier Prime", monospace;
+    font-size: 0.65rem;
+    letter-spacing: 0.06em;
+    color: #6b6454;
+  }
   .mast-room { margin-left: auto; font-size: 0.85rem; color: #a49c86; }
   .mast-room b { color: #e9e1cb; letter-spacing: 0.12em; }
   .mast-audience { font-size: 0.85rem; color: #a49c86; white-space: nowrap; }
diff --git a/packages/web/src/vite-env.d.ts b/packages/web/src/vite-env.d.ts
new file mode 100644
index 0000000..a737a71
--- /dev/null
+++ b/packages/web/src/vite-env.d.ts
@@ -0,0 +1,5 @@
+/// <reference types="vite/client" />
+/// <reference types="svelte" />
+
+/** Build moment, yyyy.mm.dd.hh.mm — injected by vite.config.ts. */
+declare const __BUILD_STAMP__: string;
diff --git a/packages/web/vite.config.ts b/packages/web/vite.config.ts
index 8a6f4b5..40c6bde 100644
--- a/packages/web/vite.config.ts
+++ b/packages/web/vite.config.ts
@@ -1,6 +1,20 @@
 import { defineConfig } from "vite";
 import { svelte } from "@sveltejs/vite-plugin-svelte";
 
+// Deploys build locally moments before rsync, so build time IS deploy time.
+const now = new Date();
+const pad = (n: number) => String(n).padStart(2, "0");
+const stamp = [
+  now.getFullYear(),
+  pad(now.getMonth() + 1),
+  pad(now.getDate()),
+  pad(now.getHours()),
+  pad(now.getMinutes()),
+].join(".");
+
 export default defineConfig({
   plugins: [svelte()],
+  define: {
+    __BUILD_STAMP__: JSON.stringify(stamp),
+  },
 });