diff --git a/web/admin.html b/web/admin.html
index 22c7e6a..27604be 100644
--- a/web/admin.html
+++ b/web/admin.html
@@ -199,6 +199,7 @@
 
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
         crossorigin="anonymous"></script>
+    <script src="assets/js/nav.js"></script>
 
     <script>
         'use strict';
diff --git a/web/assets/js/nav.js b/web/assets/js/nav.js
new file mode 100644
index 0000000..b8fa8ad
--- /dev/null
+++ b/web/assets/js/nav.js
@@ -0,0 +1,193 @@
+(function () {
+  'use strict';
+
+  // ── Track setIntervals so navigation can clear them ───────────────────────
+  const _origSetInterval  = window.setInterval.bind(window);
+  const _origClearInterval = window.clearInterval.bind(window);
+  let _intervals = [];
+
+  window.setInterval = function (fn, ms, ...args) {
+    const id = _origSetInterval(fn, ms, ...args);
+    _intervals.push(id);
+    return id;
+  };
+
+  function clearTrackedIntervals() {
+    _intervals.forEach(id => _origClearInterval(id));
+    _intervals = [];
+  }
+
+  // ── Cleanup state left behind by the outgoing page ────────────────────────
+  function cleanupPage() {
+    clearTrackedIntervals();
+
+    // DataTables 2.x
+    if (window.DataTable) {
+      try { DataTable.tables({ api: true }).destroy(); } catch (_) {}
+    }
+
+    // Dropzone
+    if (window.Dropzone) {
+      try { [...Dropzone.instances].forEach(dz => dz.destroy()); } catch (_) {}
+    }
+
+    // Bootstrap modals – hide any open one and remove leftover backdrops
+    document.querySelectorAll('.modal.show').forEach(el => {
+      try { bootstrap.Modal.getInstance(el)?.hide(); } catch (_) {}
+    });
+    document.querySelectorAll('.modal-backdrop').forEach(el => el.remove());
+    document.body.classList.remove('modal-open');
+    document.body.style.removeProperty('padding-right');
+  }
+
+  // ── Per-page inline <style> management ───────────────────────────────────
+  const STYLE_ID = 'ajax-page-style';
+  function setPageStyles(cssText) {
+    let tag = document.getElementById(STYLE_ID);
+    if (!cssText) { tag?.remove(); return; }
+    if (!tag) {
+      tag = document.createElement('style');
+      tag.id = STYLE_ID;
+      document.head.appendChild(tag);
+    }
+    tag.textContent = cssText;
+  }
+
+  // ── Load external <script src> tags not already on the page ──────────────
+  const _loadedSrcs = new Set(
+    [...document.querySelectorAll('script[src]')].map(s => s.src)
+  );
+
+  function loadScript(src) {
+    const abs = new URL(src, location.href).href;
+    if (_loadedSrcs.has(abs)) return Promise.resolve();
+    _loadedSrcs.add(abs);
+    return new Promise((resolve, reject) => {
+      const s = document.createElement('script');
+      s.src = src;
+      s.onload = resolve;
+      s.onerror = reject;
+      document.head.appendChild(s);
+    });
+  }
+
+  // ── Load external <link rel="stylesheet"> tags not already on the page ───
+  const _loadedHrefs = new Set(
+    [...document.querySelectorAll('link[rel="stylesheet"]')].map(l => l.href)
+  );
+
+  function loadStylesheet(href) {
+    const abs = new URL(href, location.href).href;
+    if (_loadedHrefs.has(abs)) return Promise.resolve();
+    _loadedHrefs.add(abs);
+    return new Promise((resolve, reject) => {
+      const l = document.createElement('link');
+      l.rel = 'stylesheet';
+      l.href = href;
+      l.onload = resolve;
+      l.onerror = reject;
+      document.head.appendChild(l);
+    });
+  }
+
+  // ── Re-execute inline scripts from the fetched document ──────────────────
+  function runInlineScripts(doc) {
+    doc.querySelectorAll('body script:not([src])').forEach(old => {
+      const code = old.textContent;
+
+      // Wrap in an IIFE so top-level `let`/`const` are function-scoped and
+      // don't collide with bindings from a previous visit to the same page.
+      // Then re-expose every named function declaration to `window` so that
+      // inline onclick="foo()" handlers continue to resolve them globally.
+      const funcNames = [
+        ...code.matchAll(/^(?:async\s+)?function\s+(\w+)\s*\(/gm),
+      ].map(m => m[1]);
+
+      const expose = funcNames
+        .map(n => `try{window.${n}=${n};}catch(_){}`)
+        .join('\n');
+
+      const s = document.createElement('script');
+      s.textContent = `(function(){\n${code}\n${expose}\n})();`;
+      document.head.appendChild(s);
+      s.remove();
+    });
+  }
+
+  // ── Update which nav link is highlighted as active ────────────────────────
+  function setActiveNav(filename) {
+    document.querySelectorAll('.nav-link-custom, .bottom-nav a').forEach(el => {
+      const hf = (el.getAttribute('href') || '').split('/').pop();
+      el.classList.toggle('active', hf === filename);
+    });
+  }
+
+  // ── Core AJAX navigation ──────────────────────────────────────────────────
+  let _navigating = false;
+
+  async function navigateTo(href) {
+    if (_navigating) return;
+    _navigating = true;
+
+    const mainInner = document.querySelector('.main-inner');
+    if (!mainInner) { window.location.href = href; return; }
+
+    // Dim content while loading
+    mainInner.style.transition = 'opacity 0.12s';
+    mainInner.style.opacity = '0.35';
+
+    try {
+      const r = await fetch(href, { redirect: 'manual' });
+      if (r.type === 'opaqueredirect') { window.location.reload(); return; }
+      if (!r.ok) { window.location.href = href; return; }
+
+      const text = await r.text();
+      const doc = new DOMParser().parseFromString(text, 'text/html');
+
+      // Load any external libs/styles the new page needs that aren't already loaded.
+      // Scripts must load sequentially (order matters: e.g. jQuery before DataTables).
+      // Stylesheets have no dependency order so can load in parallel.
+      for (const s of doc.querySelectorAll('script[src]')) {
+        await loadScript(s.getAttribute('src'));
+      }
+      await Promise.all(
+        [...doc.querySelectorAll('link[rel="stylesheet"]')].map(l => loadStylesheet(l.getAttribute('href')))
+      );
+
+      // Swap page-specific inline styles
+      const styles = [...doc.head.querySelectorAll('style')].map(s => s.textContent).join('\n');
+      setPageStyles(styles || null);
+
+      // Cleanup outgoing page, then inject new content
+      cleanupPage();
+      mainInner.innerHTML = doc.querySelector('.main-inner')?.innerHTML ?? '';
+      document.title = doc.title;
+
+      const filename = href.split('/').pop();
+      setActiveNav(filename);
+
+      // Execute the new page's inline scripts in order
+      runInlineScripts(doc);
+
+    } catch {
+      // Fallback to hard navigation on any error
+      window.location.href = href;
+    } finally {
+      mainInner.style.opacity = '1';
+      _navigating = false;
+    }
+  }
+
+  // ── Intercept all local .html link clicks ────────────────────────────────
+  document.addEventListener('click', e => {
+    const link = e.target.closest('a[href]');
+    if (!link) return;
+    const href = link.getAttribute('href');
+    if (!href || href.startsWith('#') || href.includes('://') || !href.endsWith('.html')) return;
+    e.preventDefault();
+    navigateTo(href);
+  }, true);
+
+  // History API intentionally omitted — no pushState/popstate.
+
+})();
diff --git a/web/attendees.html b/web/attendees.html
index 3f5966c..44ef5e4 100644
--- a/web/attendees.html
+++ b/web/attendees.html
@@ -194,6 +194,7 @@
 
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
         crossorigin="anonymous"></script>
+    <script src="assets/js/nav.js"></script>
     <script src="https://unpkg.com/dropzone@6.0.0-beta.1/dist/dropzone-min.js"></script>
     <script src="https://code.jquery.com/jquery-4.0.0.min.js"
         integrity="sha256-OaVG6prZf4v69dPg6PhVattBXkcOWQB62pdZ3ORyrao=" crossorigin="anonymous"></script>
diff --git a/web/delivery-log.html b/web/delivery-log.html
index 5529a86..3592bc2 100644
--- a/web/delivery-log.html
+++ b/web/delivery-log.html
@@ -120,6 +120,7 @@
 
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
     crossorigin="anonymous"></script>
+  <script src="assets/js/nav.js"></script>
   <script src="https://code.jquery.com/jquery-4.0.0.min.js"
     integrity="sha256-OaVG6prZf4v69dPg6PhVattBXkcOWQB62pdZ3ORyrao=" crossorigin="anonymous"></script>
   <script src="https://cdn.datatables.net/2.3.8/js/dataTables.min.js"></script>
diff --git a/web/index.html b/web/index.html
index 426856c..cf22e47 100644
--- a/web/index.html
+++ b/web/index.html
@@ -230,6 +230,7 @@
 
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
     crossorigin="anonymous"></script>
+  <script src="assets/js/nav.js"></script>
   <script>
     function esc(str) {
       return String(str).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
diff --git a/web/schedule.html b/web/schedule.html
index 87c787c..4c4779d 100644
--- a/web/schedule.html
+++ b/web/schedule.html
@@ -213,6 +213,7 @@
 
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
     crossorigin="anonymous"></script>
+  <script src="assets/js/nav.js"></script>
   <script>
     // ── Mode toggle ──────────────────────────────────────────
     let currentMode = 'specific';
diff --git a/web/send-now.html b/web/send-now.html
index 54b4762..830df8b 100644
--- a/web/send-now.html
+++ b/web/send-now.html
@@ -141,6 +141,7 @@
 
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
     crossorigin="anonymous"></script>
+  <script src="assets/js/nav.js"></script>
   <script>
     const SEND_MAX = 160;
 
diff --git a/web/templates.html b/web/templates.html
index a1e43b7..552a8d5 100644
--- a/web/templates.html
+++ b/web/templates.html
@@ -110,6 +110,7 @@
 
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
     crossorigin="anonymous"></script>
+  <script src="assets/js/nav.js"></script>
   <script>
     const MAX_CHARS = 160;