diff --git a/src/App.svelte b/src/App.svelte
index 46287db..4b2b57e 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -20,11 +20,13 @@
   import { loadDocumentLanguage, saveDocumentLanguage, odfFromLanguage, type DocumentLanguage } from './lib/storage/documentLanguage';
   import { spellController } from './lib/spell/controller';
   import LanguagePicker from './lib/editor/LanguagePicker.svelte';
+  import AboutDialog from './lib/AboutDialog.svelte';
 
   let editor: Editor | null = $state(null);
   let tick: number = $state(0);
   let currentPage: number = $state(1);
   let numPages: number = $state(1);
+  let aboutOpen = $state(false);
 
   // Header/footer content + live-edit state. While a zone is being edited, the
   // top toolbars target hfEditor instead of the body editor (activeEditor below).
@@ -385,7 +387,9 @@
 
 <main>
   <header class:expanded={toolbarExpanded}>
-    <img src="/PrimeText.png" alt="PrimeText" class="app-logo" />
+    <button class="logo-btn" onclick={() => (aboutOpen = true)} aria-label="About PrimeText" title="About PrimeText">
+      <img src="/PrimeText.png" alt="PrimeText" class="app-logo" />
+    </button>
     <Toolbar editor={activeEditor} tick={activeTick} />
     <div class="header-actions">
       {#snippet saveIcon()}
@@ -641,6 +645,8 @@
     </div>
     </div>
   </footer>
+
+  <AboutDialog bind:open={aboutOpen} />
 </main>
 
 <style>
@@ -667,10 +673,26 @@
     box-shadow: none;
   }
 
+  .logo-btn {
+    display: inline-flex;
+    align-items: center;
+    padding: 4px;
+    margin: 0 0.25rem 0 0.5rem;
+    border: none;
+    border-radius: var(--radius);
+    background: transparent;
+    cursor: pointer;
+    transition: background 0.12s;
+    flex-shrink: 0;
+  }
+  .logo-btn:hover {
+    background: var(--color-btn-hover);
+  }
+
   .app-logo {
     height: 17px;
     width: auto;
-    margin: 0 0.5rem 0 0.75rem;
+    display: block;
     opacity: 1.0;
     flex-shrink: 0;
   }
diff --git a/src/lib/AboutDialog.svelte b/src/lib/AboutDialog.svelte
new file mode 100644
index 0000000..9b1da9b
--- /dev/null
+++ b/src/lib/AboutDialog.svelte
@@ -0,0 +1,169 @@
+<script lang="ts">
+  // Placeholder until the project's repository is public; swap the URL when known.
+  const REPO_URL = 'https://github.com/your-org/primetext';
+
+  let { open = $bindable(false) }: { open?: boolean } = $props();
+
+  let dialogEl: HTMLDialogElement | null = $state(null);
+
+  // Drive the native <dialog> from the `open` prop so it brings backdrop,
+  // Escape-to-close, focus trapping and background inert with it.
+  $effect(() => {
+    const el = dialogEl;
+    if (!el) return;
+    if (open && !el.open) el.showModal();
+    else if (!open && el.open) el.close();
+  });
+
+  // The native close event (Escape, .close()) is the single source of truth.
+  function onClose() {
+    open = false;
+  }
+
+  // A click that lands on the dialog element itself is on the backdrop.
+  function onClick(e: MouseEvent) {
+    if (e.target === dialogEl) open = false;
+  }
+</script>
+
+<dialog
+  class="about"
+  bind:this={dialogEl}
+  onclose={onClose}
+  onclick={onClick}
+  aria-label="About PrimeText"
+>
+  <div class="card">
+    <button class="close" onclick={() => (open = false)} aria-label="Close" title="Close">
+      <svg width="14" height="14" viewBox="0 0 14 14" fill="none" aria-hidden="true">
+        <path d="M3 3l8 8M11 3l-8 8" stroke="currentColor" stroke-width="1.5" stroke-linecap="round" />
+      </svg>
+    </button>
+
+    <img class="logo" src="/PrimeText.png" alt="PrimeText" />
+
+    <p class="tagline">A private editor for OpenDocument files — runs entirely in your browser.</p>
+
+    <p class="version">Version {__APP_VERSION__}</p>
+
+    <a class="repo" href={REPO_URL} target="_blank" rel="noopener">
+      <svg width="16" height="16" viewBox="0 0 16 16" fill="currentColor" aria-hidden="true">
+        <path d="M8 .2a8 8 0 0 0-2.53 15.59c.4.07.55-.17.55-.38l-.01-1.34c-2.23.49-2.7-1.07-2.7-1.07-.36-.93-.89-1.18-.89-1.18-.72-.5.06-.49.06-.49.8.06 1.22.83 1.22.83.71 1.22 1.87.87 2.33.66.07-.52.28-.87.5-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.83-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.22 2.2.82a7.6 7.6 0 0 1 4 0c1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.52.56.83 1.28.83 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48l-.01 2.19c0 .21.15.46.55.38A8 8 0 0 0 8 .2z" />
+      </svg>
+      <span>View on GitHub</span>
+    </a>
+  </div>
+</dialog>
+
+<style>
+  .about {
+    margin: auto;
+    padding: 0;
+    border: none;
+    background: transparent;
+    max-width: none;
+    max-height: none;
+    overflow: visible;
+  }
+
+  .about::backdrop {
+    background: rgba(0, 0, 0, 0.35);
+    backdrop-filter: blur(2px);
+  }
+
+  .about[open] {
+    animation: card-in 0.15s cubic-bezier(0.215, 0.61, 0.355, 1);
+  }
+  .about[open]::backdrop {
+    animation: fade-in 0.15s ease;
+  }
+
+  @keyframes card-in {
+    from { opacity: 0; transform: scale(0.96); }
+    to { opacity: 1; transform: scale(1); }
+  }
+  @keyframes fade-in {
+    from { opacity: 0; }
+    to { opacity: 1; }
+  }
+
+  .card {
+    position: relative;
+    width: 320px;
+    box-sizing: border-box;
+    padding: 28px 24px 24px;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    text-align: center;
+    gap: 12px;
+    background: var(--color-surface);
+    color: var(--color-text);
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius);
+    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.22);
+    font-family: var(--font-sans);
+  }
+
+  .close {
+    position: absolute;
+    top: 8px;
+    right: 8px;
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    width: 26px;
+    height: 26px;
+    padding: 0;
+    border: none;
+    border-radius: var(--radius);
+    background: transparent;
+    color: var(--color-text-muted);
+    cursor: pointer;
+    transition: background 0.12s, color 0.12s;
+  }
+  .close:hover {
+    background: var(--color-btn-hover);
+    color: var(--color-text);
+  }
+
+  .logo {
+    height: 30px;
+    width: auto;
+    margin-top: 4px;
+  }
+
+  .tagline {
+    margin: 0;
+    font-size: 0.85rem;
+    line-height: 1.45;
+    color: var(--color-text-muted);
+  }
+
+  .version {
+    margin: 0;
+    font-size: 0.78rem;
+    color: var(--color-text-muted);
+  }
+
+  .repo {
+    display: inline-flex;
+    align-items: center;
+    gap: 7px;
+    margin-top: 4px;
+    padding: 7px 14px;
+    font-size: 0.82rem;
+    font-weight: 500;
+    text-decoration: none;
+    color: var(--color-text);
+    background: transparent;
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius);
+    transition: border-color 0.12s, background 0.12s, color 0.12s;
+  }
+  .repo:hover {
+    background: var(--color-primary);
+    border-color: var(--color-primary);
+    color: #fff;
+  }
+</style>
diff --git a/src/vite-env.d.ts b/src/vite-env.d.ts
index 4078e74..d5ec77e 100644
--- a/src/vite-env.d.ts
+++ b/src/vite-env.d.ts
@@ -1,2 +1,4 @@
 /// <reference types="svelte" />
 /// <reference types="vite/client" />
+
+declare const __APP_VERSION__: string;
diff --git a/vite.config.ts b/vite.config.ts
index 0cf4613..39dc9c8 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -1,6 +1,8 @@
 import { defineConfig } from 'vite';
 import { svelte } from '@sveltejs/vite-plugin-svelte';
+import pkg from './package.json' with { type: 'json' };
 
 export default defineConfig({
   plugins: [svelte()],
+  define: { __APP_VERSION__: JSON.stringify(pkg.version) },
 });