diff --git a/app/config.yml b/app/config.yml
index bd20241..06b717a 100644
--- a/app/config.yml
+++ b/app/config.yml
@@ -21,6 +21,59 @@ languages:
     name: Norsk
     direction: ltr
 
+# ── About modal ───────────────────────────────────────────────────────────────
+# Optional. Remove this section entirely to hide the About link in the footer.
+# Each language entry requires: title, content (Markdown), btn-close.
+about:
+  en:
+    title: "About"
+    content: |
+      ### Invoice Generator
+      A single-file browser app for generating freelance invoices as PDF or print preview.
+      No backend, no build step — just a browser and a config file.
+
+      **Source:** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Docs:** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Licensed under the Apache 2 license.
+    btn-close: "Close"
+  de:
+    title: "Über"
+    content: |
+      ### Rechnungsgenerator
+      Eine Single-File-Browser-App zur Erstellung von Freiberufler-Rechnungen als PDF oder Druckvorschau.
+      Kein Backend, kein Build-Schritt.
+
+      **Quellcode:** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Dokumentation:** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Lizenziert unter Apache 2.
+    btn-close: "Schließen"
+  fr:
+    title: "À propos"
+    content: |
+      ### Générateur de factures
+      Une application de navigateur en fichier unique pour générer des factures en PDF ou aperçu avant impression.
+      Aucun backend, aucune étape de build.
+
+      **Code source :** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Documentation :** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Sous licence Apache 2.
+    btn-close: "Fermer"
+  "no":
+    title: "Om"
+    content: |
+      ### Fakturagenerator
+      En nettleserapp i én fil for å generere frilansfakturaer som PDF eller utskriftsforhåndsvisning.
+      Ingen backend, ingen byggtrinn.
+
+      **Kildekode:** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Dokumentasjon:** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Lisensiert under Apache 2.
+    btn-close: "Lukk"
+
 # ── Payment info visibility ───────────────────────────────────────────────────
 # Set to true to hide the payment info panel entirely (useful if payment info
 # should not appear on invoices, e.g. per company policy).
diff --git a/app/index.html b/app/index.html
index c1f680d..f9fc83d 100644
--- a/app/index.html
+++ b/app/index.html
@@ -220,6 +220,41 @@
     /* ── Error / loading ────────────────────────────────────────────────────── */
     #loading { padding: 48px; text-align: center; color: var(--text-muted); font-size: 14px; }
     .error-box { background: #fef2f2; border: 1px solid #fca5a5; color: #991b1b; padding: 16px 20px; border-radius: var(--radius); margin: 20px 0; font-size: 13px; }
+
+    /* ── Footer ─────────────────────────────────────────────────────────────── */
+    #app-footer { text-align: center; font-size: 11px; color: var(--text-muted); padding: 18px 0 24px; }
+    #app-footer a { color: var(--text-muted); text-decoration: none; }
+    #app-footer a:hover { color: var(--accent); text-decoration: underline; }
+
+    /* ── About modal ────────────────────────────────────────────────────────── */
+    #about-modal { display: none; position: fixed; inset: 0; z-index: 1000; }
+    #about-overlay { position: absolute; inset: 0; background: rgba(0,0,0,.45); }
+    #about-dialog {
+      position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%);
+      background: var(--white); border-radius: 6px; box-shadow: 0 20px 60px rgba(0,0,0,.25);
+      width: min(560px, 92vw); max-height: 80vh; display: flex; flex-direction: column;
+    }
+    #about-dialog-header {
+      padding: 18px 20px 14px; border-bottom: 1px solid var(--border);
+      font-size: 15px; font-weight: 700; color: var(--navy);
+    }
+    #about-dialog-body {
+      padding: 16px 20px; overflow-y: auto; font-size: 13px; line-height: 1.6; color: var(--text);
+    }
+    #about-dialog-body h1,#about-dialog-body h2,#about-dialog-body h3 {
+      font-size: 13px; font-weight: 700; margin: 12px 0 4px; color: var(--navy);
+    }
+    #about-dialog-body p { margin-bottom: 8px; }
+    #about-dialog-body a { color: var(--accent); }
+    #about-dialog-body ul,#about-dialog-body ol { padding-left: 20px; margin-bottom: 8px; }
+    #about-dialog-footer {
+      padding: 12px 20px; border-top: 1px solid var(--border); text-align: right;
+    }
+    #about-btn-close {
+      background: var(--navy); color: var(--white); border: none; border-radius: var(--radius);
+      font-size: 13px; padding: 6px 18px; cursor: pointer;
+    }
+    #about-btn-close:hover { background: var(--accent); }
   </style>
 </head>
 <body>
@@ -246,8 +281,23 @@
   <!-- Main form (injected by JS) -->
   <div id="form-root"></div>
 
+  <!-- Footer -->
+  <footer id="app-footer"></footer>
+
 </div><!-- /.wrap -->
 
+<!-- About modal (outside .wrap so it overlays everything) -->
+<div id="about-modal" role="dialog" aria-modal="true">
+  <div id="about-overlay" onclick="closeAbout()"></div>
+  <div id="about-dialog">
+    <div id="about-dialog-header"></div>
+    <div id="about-dialog-body"></div>
+    <div id="about-dialog-footer">
+      <button id="about-btn-close" onclick="closeAbout()">Close</button>
+    </div>
+  </div>
+</div>
+
 
 <!-- js-yaml -->
 <script src="https://cdnjs.cloudflare.com/ajax/libs/js-yaml/4.1.0/js-yaml.min.js"
@@ -255,6 +305,9 @@
 <!-- jsPDF -->
 <script src="https://cdnjs.cloudflare.com/ajax/libs/jspdf/2.5.1/jspdf.umd.min.js"
         crossorigin="anonymous"></script>
+<!-- marked -->
+<script src="https://cdnjs.cloudflare.com/ajax/libs/marked/9.1.6/marked.min.js"
+        crossorigin="anonymous"></script>
 
 <script>
 "use strict";
@@ -416,6 +469,7 @@ async function loadCfg() {
 function boot() {
   buildLangBar();
   buildForm();
+  buildFooter();
   restoreStorage();
   if (!loadLines()) addLine();
   document.getElementById("loading").style.display = "none";
@@ -1088,6 +1142,7 @@ function relabel() {
     ctPick.value = cur;
   }
 
+  buildFooter();
 }
 
 // ── Generate invoice ──────────────────────────────────────────────────────────
@@ -1541,6 +1596,46 @@ function resetLines() {
   calcTotals();
 }
 
+// ── Footer & About modal ──────────────────────────────────────────────────────
+function aboutData() {
+  const ab = cfg?.about;
+  if (!ab) return null;
+  return ab[lang] ?? ab[cfg["default-code"]] ?? Object.values(ab)[0] ?? null;
+}
+
+function buildFooter() {
+  const footer = document.getElementById("app-footer");
+  if (!footer) return;
+  const ab = aboutData();
+  const aboutLink = ab
+    ? ` &bull; <a href="#" onclick="openAbout();return false">${h(ab.title ?? "About")}</a>`
+    : "";
+  footer.innerHTML =
+    `&copy; 2026 Kristian Benestad`
+    + ` &bull; <a href="https://docs.benestad.net/invoice" target="_blank" rel="noopener">docs.benestad.net</a>`
+    + ` &bull; <a href="https://github.com/kbenestad/invoice" target="_blank" rel="noopener">kbenestad/invoice</a>`
+    + aboutLink;
+}
+
+function openAbout() {
+  const ab = aboutData();
+  if (!ab) return;
+  document.getElementById("about-dialog-header").textContent = ab.title ?? "";
+  document.getElementById("about-dialog-body").innerHTML =
+    typeof marked !== "undefined" ? marked.parse(ab.content ?? "") : h(ab.content ?? "");
+  document.getElementById("about-btn-close").textContent = ab["btn-close"] ?? "Close";
+  document.getElementById("about-modal").style.display = "block";
+  document.getElementById("about-btn-close").focus();
+}
+
+function closeAbout() {
+  document.getElementById("about-modal").style.display = "none";
+}
+
+document.addEventListener("keydown", e => {
+  if (e.key === "Escape") closeAbout();
+});
+
 // ── Start ─────────────────────────────────────────────────────────────────────
 loadCfg();
 </script>