diff --git a/dDashboardServer/static/css/dashboard.css b/dDashboardServer/static/css/dashboard.css
index c1451cfcf..9e9c0fdc2 100644
--- a/dDashboardServer/static/css/dashboard.css
+++ b/dDashboardServer/static/css/dashboard.css
@@ -233,3 +233,8 @@ details.about-text > summary::before {
 details.about-text > summary:hover { color: var(--bs-body-color); }
 details.about-text[open] > summary { margin-bottom: .35rem; }
 details.about-text > :not(summary) { color: var(--bs-secondary-color); font-size: .875rem; }
+
+/* Wide screens: the menu can be hidden (the top bar's menu button; header.jinja2 keeps the choice) */
+@media (min-width: 992px) {
+	html.sidebar-hidden nav.sidebar { display: none !important; }
+}
diff --git a/dDashboardServer/templates/base.jinja2 b/dDashboardServer/templates/base.jinja2
index cf88929b6..322e06060 100644
--- a/dDashboardServer/templates/base.jinja2
+++ b/dDashboardServer/templates/base.jinja2
@@ -5,6 +5,8 @@
 	<meta name="viewport" content="width=device-width, initial-scale=1.0">
 	<title>{% block title %}DarkflameServer{% endblock %}</title>
 	<link rel="icon" href="data:,">
+	{# The menu hidden on wide screens stays hidden from page to page (header.jinja2), set before the first paint #}
+	<script>try { if ((JSON.parse(localStorage.getItem('dash.sidebar') || '{}') || {}).hidden) document.documentElement.classList.add('sidebar-hidden'); } catch (e) {}</script>
 	<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/5.3.0/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-9ndCyUaIbzAi2FUVXJi0CjmCapSmO7SnpJef0486qhLnuZ2cdeRhO02iuK6FUUVM" crossorigin="anonymous">
 	<link href="https://cdn.datatables.net/v/bs5/jq-3.7.0/dt-2.3.7/b-3.2.6/fh-4.0.6/sc-2.4.3/datatables.min.css" rel="stylesheet" integrity="sha384-XMNDGLb5fN9IqhIrVXOAtGKcz4KCr+JSHXGZ1TDXQPDukbEAfmLPjHdCXhgK93fv" crossorigin="anonymous">
 	<link rel="stylesheet" href="/css/dashboard.css">
@@ -17,6 +19,7 @@
 		<div class="flex-grow-1 d-flex flex-column min-vh-100 main-column">
 			<header class="topbar d-flex align-items-center gap-2 border-bottom px-3 py-2 sticky-top bg-body-tertiary">
 				<button class="btn btn-sm btn-outline-secondary d-lg-none" type="button" data-bs-toggle="offcanvas" data-bs-target="#sidebar" aria-controls="sidebar">&#9776; Menu</button>
+				<button class="btn btn-sm btn-outline-secondary d-none d-lg-inline-block sidebar-toggle" type="button" data-sidebar-toggle aria-controls="sidebar" title="Show or hide the menu"><span aria-hidden="true">&#9776;</span><span class="visually-hidden">Show or hide the menu</span></button>
 				<a href="/" class="fw-semibold text-body text-decoration-none d-lg-none">DarkflameServer</a>
 				<div class="dropdown ms-auto">
 					<button class="btn btn-sm btn-link text-body text-decoration-none dropdown-toggle d-flex align-items-center gap-2" type="button" data-bs-toggle="dropdown" aria-expanded="false">
diff --git a/dDashboardServer/templates/header.jinja2 b/dDashboardServer/templates/header.jinja2
index e4f526a3d..9cab77c46 100644
--- a/dDashboardServer/templates/header.jinja2
+++ b/dDashboardServer/templates/header.jinja2
@@ -1,7 +1,8 @@
 {# Sidebar navigation. Entries show only with the permission their page needs (see Permissions.cpp). #}
 {# Grouped by what staff are doing: the most used pages always show, the rest sit in groups that fold away (the group of #}
 {# the current page starts open). Inbox holds what players sent in and staff still have to answer. #}
-{# On narrow screens this is a slide-out menu opened from the top bar in base.jinja2 #}
+{# On narrow screens this is a slide-out menu opened from the top bar in base.jinja2. Which groups are open, and whether #}
+{# the menu is hidden on wide screens, is kept in this browser (the script at the end, and the <head> of base.jinja2) #}
 <nav class="offcanvas-lg offcanvas-start d-flex flex-column flex-shrink-0 px-2 py-3 border-end sidebar" id="sidebar" tabindex="-1" aria-label="Navigation">
 	<div class="d-flex align-items-center justify-content-between px-2 mb-3">
 		<a href="/" class="text-decoration-none text-body"><span class="fs-5 fw-semibold">DarkflameServer</span></a>
@@ -155,3 +156,57 @@
 	</div>
 	{% endif %}
 </nav>
+<script data-sidebar-state>
+/*
+ * The sidebar's groups open or closed as they were last left, in this browser (localStorage "dash.sidebar":
+ * {groups: {id: open}, hidden}). Runs right after the menu is parsed, before the first paint, so it never shows the
+ * server's default first. The group holding the current page always opens, and stays open on the next page until it
+ * is closed. Sidebar.apply() does it again after the page changes without a reload (nav.js); Sidebar.setHidden()
+ * hides the menu on wide screens.
+ */
+window.Sidebar = (function () {
+	var KEY = 'dash.sidebar';
+	function load() {
+		try { var s = JSON.parse(localStorage.getItem(KEY) || '{}'); return s && typeof s === 'object' ? s : {}; } catch (e) { return {}; }
+	}
+	function save(state) { try { localStorage.setItem(KEY, JSON.stringify(state)); } catch (e) { /* storage unavailable */ } }
+	function setOpen(el, open) {
+		el.classList.toggle('show', open);
+		document.querySelectorAll('[data-bs-target="#' + el.id + '"]').forEach(function (b) {
+			b.classList.toggle('collapsed', !open);
+			b.setAttribute('aria-expanded', open ? 'true' : 'false');
+		});
+	}
+	function apply() {
+		var state = load();
+		var groups = state.groups = state.groups || {};
+		document.querySelectorAll('#sidebar .nav-group > .collapse[id]').forEach(function (el) {
+			var open = (el.id in groups ? !!groups[el.id] : el.classList.contains('show')) || !!el.querySelector('.active');
+			setOpen(el, open);
+			groups[el.id] = open;
+		});
+		save(state);
+	}
+	function remember(e) {
+		var el = e.target;
+		if (!el.id || !el.closest || !el.closest('#sidebar')) return;
+		var state = load();
+		state.groups = state.groups || {};
+		state.groups[el.id] = e.type === 'shown.bs.collapse';
+		save(state);
+	}
+	function setHidden(hidden) {
+		var state = load();
+		state.hidden = !!hidden;
+		save(state);
+		document.documentElement.classList.toggle('sidebar-hidden', !!hidden);
+	}
+	apply();
+	document.addEventListener('shown.bs.collapse', remember);
+	document.addEventListener('hidden.bs.collapse', remember);
+	document.addEventListener('click', function (e) {
+		if (e.target.closest && e.target.closest('[data-sidebar-toggle]')) setHidden(!document.documentElement.classList.contains('sidebar-hidden'));
+	});
+	return { apply: apply, setHidden: setHidden, load: load };
+})();
+</script>
diff --git a/docs/Dashboard.md b/docs/Dashboard.md
index 704321f2c..6b0b314d7 100644
--- a/docs/Dashboard.md
+++ b/docs/Dashboard.md
@@ -366,6 +366,9 @@ unless you're typing, in which case they offer a refresh instead.
 View choices you make on the pages (show staff, filters, the 3D viewer's switches, ...) are saved to your account, so
 they follow you to other browsers.
 
+The menu's groups stay open or closed from page to page (kept in this browser): the group of the page you're on opens
+and stays open until you close it. On wide screens the &#9776; button in the top bar hides the menu, and it stays hidden until you show it again.
+
 On narrow screens the menu folds into a **Menu** button, and the moderation queues and online players show as cards
 with their buttons, so you can approve names or kick someone from a phone.
 
diff --git a/tests/dWebTests/CMakeLists.txt b/tests/dWebTests/CMakeLists.txt
index 62707f553..9709f8604 100644
--- a/tests/dWebTests/CMakeLists.txt
+++ b/tests/dWebTests/CMakeLists.txt
@@ -91,4 +91,7 @@ if(NODE_EXECUTABLE)
 	add_test(NAME SceneryCoreJs COMMAND ${NODE_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/scenery-core.test.mjs"
 		"${PROJECT_SOURCE_DIR}/dDashboardServer/static/js/scenery-core.js" "${PROJECT_SOURCE_DIR}/dCommon/NifFile.h"
 		"${PROJECT_SOURCE_DIR}/dDashboardServer/routes/Scenery.cpp")
+	# The sidebar's saved group state (the script at the end of templates/header.jinja2)
+	add_test(NAME SidebarStateJs COMMAND ${NODE_EXECUTABLE} "${CMAKE_CURRENT_SOURCE_DIR}/sidebar-state.test.mjs"
+		"${PROJECT_SOURCE_DIR}/dDashboardServer/templates/header.jinja2")
 endif()
diff --git a/tests/dWebTests/sidebar-state.test.mjs b/tests/dWebTests/sidebar-state.test.mjs
new file mode 100644
index 000000000..3ae9aa887
--- /dev/null
+++ b/tests/dWebTests/sidebar-state.test.mjs
@@ -0,0 +1,108 @@
+// The sidebar's saved group state (the <script data-sidebar-state> in templates/header.jinja2), run on a small fake DOM.
+// Run by ctest: node sidebar-state.test.mjs <header.jinja2>
+import { readFileSync } from 'node:fs';
+import vm from 'node:vm';
+
+const [headerPath] = process.argv.slice(2);
+const source = readFileSync(headerPath, 'utf8').match(/<script data-sidebar-state>([\s\S]*?)<\/script>/)[1];
+let failures = 0;
+const same = (actual, expected, what) => {
+	if (JSON.stringify(actual) !== JSON.stringify(expected)) {
+		failures++;
+		console.error(`${what}: ${JSON.stringify(actual)} is not ${JSON.stringify(expected)}`);
+	}
+};
+
+class ClassList {
+	constructor(names) { this.set = new Set(names); }
+	contains(n) { return this.set.has(n); }
+	toggle(n, on) { if (on === undefined) on = !this.set.has(n); if (on) this.set.add(n); else this.set.delete(n); return on; }
+	add(n) { this.set.add(n); }
+}
+
+// A sidebar with three groups; "nav-logs" holds the current page
+function page(storage, shownByServer) {
+	const groups = ['nav-inbox', 'nav-world', 'nav-logs'].map((id) => ({
+		id,
+		classList: new ClassList(shownByServer.includes(id) ? ['collapse', 'show'] : ['collapse']),
+		querySelector: (sel) => (sel === '.active' && id === 'nav-logs' ? {} : null),
+		closest: (sel) => (sel === '#sidebar' ? {} : null)
+	}));
+	const toggles = Object.fromEntries(groups.map((g) => [g.id, { classList: new ClassList([]), attrs: {}, setAttribute(k, v) { this.attrs[k] = v; } }]));
+	const listeners = {};
+	const html = { classList: new ClassList([]) };
+	const document = {
+		documentElement: html,
+		querySelectorAll(sel) {
+			if (sel === '#sidebar .nav-group > .collapse[id]') return groups;
+			const m = sel.match(/^\[data-bs-target="#(.+)"\]$/);
+			return m ? [toggles[m[1]]] : [];
+		},
+		addEventListener(type, fn) { (listeners[type] = listeners[type] || []).push(fn); }
+	};
+	const localStorage = {
+		getItem: (k) => (k in storage ? storage[k] : null),
+		setItem: (k, v) => { storage[k] = String(v); }
+	};
+	const window = {};
+	vm.runInNewContext(source, { window, document, localStorage, JSON });
+	const open = () => Object.fromEntries(groups.map((g) => [g.id, g.classList.contains('show')]));
+	const fire = (type, id) => (listeners[type] || []).forEach((fn) => fn({ type, target: groups.find((g) => g.id === id) }));
+	return { window, open, fire, toggles, html, listeners };
+}
+
+// Nothing saved: the server's choice (the current page's group) stays, and is kept for the next page
+{
+	const storage = {};
+	const p = page(storage, ['nav-logs']);
+	same(p.open(), { 'nav-inbox': false, 'nav-world': false, 'nav-logs': true }, 'nothing saved');
+	same(JSON.parse(storage['dash.sidebar']).groups, { 'nav-inbox': false, 'nav-world': false, 'nav-logs': true }, 'kept');
+}
+
+// Opening and closing groups is saved, and the next page starts that way
+{
+	const storage = {};
+	const p = page(storage, ['nav-logs']);
+	p.fire('shown.bs.collapse', 'nav-world');
+	p.fire('hidden.bs.collapse', 'nav-inbox');
+	same(JSON.parse(storage['dash.sidebar']).groups, { 'nav-inbox': false, 'nav-world': true, 'nav-logs': true }, 'saved groups');
+	const next = page(storage, ['nav-logs']);
+	same(next.open(), { 'nav-inbox': false, 'nav-world': true, 'nav-logs': true }, 'next page');
+	same(next.toggles['nav-world'].attrs['aria-expanded'], 'true', 'toggle follows the group');
+	same(next.toggles['nav-inbox'].classList.contains('collapsed'), true, 'closed toggle marked collapsed');
+}
+
+// A group left open on another page stays open here
+{
+	const p = page({ 'dash.sidebar': JSON.stringify({ groups: { 'nav-inbox': true, 'nav-world': false } }) }, ['nav-logs']);
+	same(p.open(), { 'nav-inbox': true, 'nav-world': false, 'nav-logs': true }, 'left open');
+}
+
+// The current page's group opens even when it was closed last time
+{
+	const p = page({ 'dash.sidebar': JSON.stringify({ groups: { 'nav-logs': false, 'nav-inbox': true } }) }, []);
+	same(p.open(), { 'nav-inbox': true, 'nav-world': false, 'nav-logs': true }, 'current group opens');
+}
+
+// Broken or blocked storage: the server's choice
+{
+	const p = page({ 'dash.sidebar': '{nope' }, ['nav-inbox']);
+	same(p.open(), { 'nav-inbox': true, 'nav-world': false, 'nav-logs': true }, 'broken storage');
+}
+
+// Hiding the menu is saved with the groups
+{
+	const storage = { 'dash.sidebar': JSON.stringify({ groups: { 'nav-world': true } }) };
+	const p = page(storage, []);
+	p.window.Sidebar.setHidden(true);
+	same(JSON.parse(storage['dash.sidebar']), { groups: { 'nav-world': true, 'nav-inbox': false, 'nav-logs': true }, hidden: true }, 'hidden saved');
+	same(p.html.classList.contains('sidebar-hidden'), true, 'hidden now');
+	p.window.Sidebar.setHidden(false);
+	same(p.html.classList.contains('sidebar-hidden'), false, 'shown again');
+}
+
+if (failures) {
+	console.error(`${failures} failure(s)`);
+	process.exit(1);
+}
+console.log('sidebar state: all passed');