diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index 543b6c3..c8b57ab 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "ds-chat"
-version = "0.1.0"
+version = "1.0.0"
 description = "DS Chat backend service"
 license = { text = "AGPL-3.0-or-later" }
 requires-python = ">=3.11"
diff --git a/frontend/package.json b/frontend/package.json
index ab4cf99..e483b35 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -1,7 +1,7 @@
 {
   "name": "frontend",
   "private": true,
-  "version": "0.0.0",
+  "version": "1.0.0",
   "license": "AGPL-3.0-or-later",
   "type": "module",
   "scripts": {
diff --git a/frontend/public/LICENSE b/frontend/public/LICENSE
new file mode 120000
index 0000000..30cff74
--- /dev/null
+++ b/frontend/public/LICENSE
@@ -0,0 +1 @@
+../../LICENSE
\ No newline at end of file
diff --git a/frontend/src/components/AboutModal.css b/frontend/src/components/AboutModal.css
new file mode 100644
index 0000000..39e55cc
--- /dev/null
+++ b/frontend/src/components/AboutModal.css
@@ -0,0 +1,27 @@
+.about-modal-brand {
+  display: flex;
+  align-items: center;
+  gap: var(--sp-3);
+  margin-bottom: var(--sp-4);
+}
+
+.about-modal-logo {
+  width: 40px;
+  height: 40px;
+  flex: none;
+}
+
+.about-modal-name {
+  font-weight: 700;
+  font-size: 1.05rem;
+}
+
+.about-modal-version {
+  color: var(--ds-muted);
+  font-size: 0.85rem;
+}
+
+.about-modal-line {
+  margin: 0 0 var(--sp-2);
+  font-size: 0.9rem;
+}
diff --git a/frontend/src/components/AboutModal.tsx b/frontend/src/components/AboutModal.tsx
new file mode 100644
index 0000000..bb0eab3
--- /dev/null
+++ b/frontend/src/components/AboutModal.tsx
@@ -0,0 +1,56 @@
+import logo from '../assets/logo.png'
+import './Modal.css'
+import './AboutModal.css'
+
+interface AboutModalProps {
+  onClose: () => void
+}
+
+// AGPL-3.0 itself recommends this: "if your software can interact with
+// users remotely through a computer network, you should also make sure
+// that it provides a way for users to get its source... its interface
+// could display a 'Source' link" -- this modal is that link, not just a
+// courtesy credits screen.
+const SOURCE_URL = 'https://git.darksingularity.org/DarkSingularity/ds-chat'
+
+export function AboutModal({ onClose }: AboutModalProps) {
+  return (
+    <div className="modal-scrim" onClick={onClose}>
+      <div className="modal about-modal" onClick={(e) => e.stopPropagation()}>
+        <div className="modal-header">
+          <h2>About</h2>
+          <button type="button" className="modal-close" onClick={onClose} aria-label="Close">
+            &times;
+          </button>
+        </div>
+
+        <div className="about-modal-brand">
+          <img src={logo} alt="" className="about-modal-logo" />
+          <div>
+            <div className="about-modal-name">DS Chat</div>
+            <div className="about-modal-version">Version {__APP_VERSION__}</div>
+          </div>
+        </div>
+
+        <p className="about-modal-line">
+          Licensed under the{' '}
+          <a href="/LICENSE" target="_blank" rel="noopener noreferrer">
+            GNU Affero General Public License v3.0 (or later)
+          </a>
+          .
+        </p>
+        <p className="about-modal-line">
+          <a href={SOURCE_URL} target="_blank" rel="noopener noreferrer">
+            Source code
+          </a>
+        </p>
+
+        <div className="modal-actions" style={{ marginTop: '1rem' }}>
+          <button type="button" className="btn-secondary" onClick={onClose}>
+            Close
+          </button>
+        </div>
+      </div>
+    </div>
+  )
+}
diff --git a/frontend/src/components/TopBar.tsx b/frontend/src/components/TopBar.tsx
index 2d9d7ca..22f523c 100644
--- a/frontend/src/components/TopBar.tsx
+++ b/frontend/src/components/TopBar.tsx
@@ -12,6 +12,7 @@ import {
   setDesktopNotificationsEnabled,
 } from '../lib/desktopBridge'
 import { getPushSubscriptionStatus, isPushSupported, subscribeToPush, unsubscribeFromPush } from '../lib/push'
+import { AboutModal } from './AboutModal'
 import { ProfileModal } from './ProfileModal'
 import { UserAvatar } from './UserAvatar'
 import './TopBar.css'
@@ -27,6 +28,7 @@ export function TopBar() {
   const navigate = useNavigate()
   const [menuOpen, setMenuOpen] = useState(false)
   const [profileModalOpen, setProfileModalOpen] = useState(false)
+  const [aboutModalOpen, setAboutModalOpen] = useState(false)
   const [pushSubscribed, setPushSubscribed] = useState(false)
   const [pushBusy, setPushBusy] = useState(false)
   const [pushError, setPushError] = useState<string | null>(null)
@@ -132,6 +134,16 @@ export function TopBar() {
               >
                 Help
               </button>
+              <button
+                type="button"
+                role="menuitem"
+                onClick={() => {
+                  setMenuOpen(false)
+                  setAboutModalOpen(true)
+                }}
+              >
+                About
+              </button>
               <button
                 type="button"
                 role="menuitem"
@@ -178,6 +190,7 @@ export function TopBar() {
         )}
       </div>
       {profileModalOpen && <ProfileModal onClose={() => setProfileModalOpen(false)} />}
+      {aboutModalOpen && <AboutModal onClose={() => setAboutModalOpen(false)} />}
     </header>
   )
 }
diff --git a/frontend/src/vite-env.d.ts b/frontend/src/vite-env.d.ts
index ec878b7..548504e 100644
--- a/frontend/src/vite-env.d.ts
+++ b/frontend/src/vite-env.d.ts
@@ -1,2 +1,5 @@
 /// <reference types="vite/client" />
 /// <reference types="vite-plugin-pwa/react" />
+
+// Injected by vite.config.ts's `define`, from package.json's version field.
+declare const __APP_VERSION__: string
diff --git a/frontend/vite.config.ts b/frontend/vite.config.ts
index b54a58b..780092d 100644
--- a/frontend/vite.config.ts
+++ b/frontend/vite.config.ts
@@ -1,9 +1,18 @@
+import { readFileSync } from 'node:fs'
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
 import { VitePWA } from 'vite-plugin-pwa'
 
+// Single source of truth for the version shown in the app's About dialog --
+// read at build time so it can never drift from what's actually released,
+// rather than a separately-maintained string in the component itself.
+const { version } = JSON.parse(readFileSync(new URL('./package.json', import.meta.url), 'utf-8'))
+
 // https://vite.dev/config/
 export default defineConfig({
+  define: {
+    __APP_VERSION__: JSON.stringify(version),
+  },
   plugins: [
     react(),
     VitePWA({