diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 92b841f4..706b710f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -236,6 +236,10 @@ jobs:
         run: |
           tar -C "spec${baseURL}" --strip-components=1 -xzf openapi.tar.gz
 
+      - name: "🔍 pagefind indexing"
+        run: |
+          npx -y pagefind --site "spec${baseURL}"
+
       - name: "📦 Tarball creation"
         run: |
           cd spec
diff --git a/assets/js/offline-search.js b/assets/js/offline-search.js
new file mode 100644
index 00000000..0a5dd267
--- /dev/null
+++ b/assets/js/offline-search.js
@@ -0,0 +1,164 @@
+/*
+Copyright 2026 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/*
+Adapted from [1] to combine Docsy's built-in search UI with the Pagefind
+search backend.
+
+  [1]: https://github.com/matrix-org/docsy/blob/71d103ebb20ace3d528178c4b6d92b6cc4f7fd53/assets/js/offline-search.js
+*/
+
+(function ($) {
+  'use strict';
+
+  $(document).ready(async function () {
+    const pagefind = await import("/pagefind/pagefind.js");
+    const $searchInput = $('.td-search input');
+
+    //
+    // Lazily initialise Pagefind only when the user is about to start a search.
+    //
+
+    $searchInput.focus(() => {
+      pagefind.init();
+    });
+
+    //
+    // Register handler
+    //
+
+    $searchInput.on('change', (event) => {
+      render($(event.target));
+
+      // Hide keyboard on mobile browser
+      $searchInput.blur();
+    });
+
+    // Prevent reloading page by enter key on sidebar search.
+    $searchInput.closest('form').on('submit', () => {
+      return false;
+    });
+
+    //
+    // Pagefind
+    //
+
+    const render = async ($targetSearchInput) => {
+      //
+      // Dispose existing popover
+      //
+
+      {
+        let popover = bootstrap.Popover.getInstance($targetSearchInput[0]);
+        if (popover !== null) {
+          popover.dispose();
+        }
+      }
+
+      //
+      // Search
+      //
+
+      const searchQuery = $targetSearchInput.val();
+      if (searchQuery === '') {
+        return;
+      }
+
+      const search = await pagefind.debouncedSearch(searchQuery);
+      if (search === null) {
+        // A more recent search call has been made, nothing to do.
+        return;
+      }
+      const results = await Promise.all(search.results.slice(0, 20).map(r => r.data()));
+
+      //
+      // Make result html
+      //
+
+      const $html = $('<div>');
+
+      $html.append(
+        $('<div>')
+          .css({
+            display: 'flex',
+            justifyContent: 'space-between',
+            marginBottom: '1em',
+          })
+          .append(
+            $('<span>').text('Search results').css({ fontWeight: 'bold' })
+          )
+          .append(
+            $('<span>').addClass('td-offline-search-results__close-button')
+          )
+      );
+
+      const $searchResultBody = $('<div>').css({
+        maxHeight: `calc(100vh - ${
+          $targetSearchInput.offset().top - $(window).scrollTop() + 180
+        }px)`,
+        overflowY: 'auto',
+      });
+      $html.append($searchResultBody);
+
+      if (results.length === 0) {
+        $searchResultBody.append(
+          $('<p>').text(`No results found for query "${searchQuery}"`)
+        );
+      } else {
+        results.forEach((r) => {
+          r.sub_results.forEach((s) => {
+            const href = s.url;
+
+            const $entry = $('<div>').addClass('mt-4');
+
+            $entry.append(
+              $('<small>').addClass('d-block text-body-secondary').text(r.meta.title)
+            );
+
+            $entry.append(
+              $('<a>')
+                .addClass('d-block')
+                .css({
+                  fontSize: '1.2rem',
+                })
+                .attr('href', href)
+                .text(s.title)
+            );
+
+            $entry.append($('<p>').html(s.excerpt));
+
+            $searchResultBody.append($entry);
+          });
+        });
+      }
+
+      $targetSearchInput.one('shown.bs.popover', () => {
+        $('.td-offline-search-results__close-button').on('click', () => {
+          $targetSearchInput.val('');
+          $targetSearchInput.trigger('change');
+        });
+      });
+
+      const popover = new bootstrap.Popover($targetSearchInput, {
+        content: $html[0],
+        html: true,
+        customClass: 'td-offline-search-results',
+        placement: 'bottom',
+      });
+      popover.show();
+    };
+  });
+})(jQuery);
diff --git a/assets/scss/_styles_project.scss b/assets/scss/_styles_project.scss
index cd9937a9..a2daa0ae 100644
--- a/assets/scss/_styles_project.scss
+++ b/assets/scss/_styles_project.scss
@@ -661,3 +661,8 @@ dd {
     margin: 0;
   }
 }
+
+/* Style for the page search widget */
+.td-offline-search-results {
+  max-width: 460px;
+}
diff --git a/changelogs/internal/newsfragments/2331.feature b/changelogs/internal/newsfragments/2331.feature
new file mode 100644
index 00000000..eb94a36e
--- /dev/null
+++ b/changelogs/internal/newsfragments/2331.feature
@@ -0,0 +1 @@
+Add page search widget.
diff --git a/config/_default/hugo.toml b/config/_default/hugo.toml
index a33f803b..8c8d9228 100644
--- a/config/_default/hugo.toml
+++ b/config/_default/hugo.toml
@@ -66,6 +66,7 @@ description = "Home of the Matrix specification for decentralised communication"
 
 [params]
 copyright = "The Matrix.org Foundation C.I.C."
+offlineSearch = true
 
 [params.version]
 # must be one of "unstable", "current", "historical"
@@ -151,7 +152,8 @@ sidebar_menu_compact = true
   [server.headers.values]
     # `style-src 'unsafe-inline'` is needed to correctly render the maths in the Olm spec:
     # https://github.com/KaTeX/KaTeX/issues/4096
-    Content-Security-Policy = "default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self'; img-src 'self' data:; connect-src 'self'; font-src 'self' data:; media-src 'self'; child-src 'self'; form-action 'self'; object-src 'self'"
+    # TODO: Figure out CSP to allow loading the Pagefind Wasm
+    #Content-Security-Policy = "default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self'; img-src 'self' data:; connect-src 'self'; font-src 'self' data:; media-src 'self'; child-src 'self'; form-action 'self'; object-src 'self'"
     X-XSS-Protection = "1; mode=block"
     X-Content-Type-Options = "nosniff"
     # Strict-Transport-Security = "max-age=31536000; includeSubDomains; preload"
diff --git a/layouts/_partials/search-input.html b/layouts/_partials/search-input.html
new file mode 100644
index 00000000..1b9b82e1
--- /dev/null
+++ b/layouts/_partials/search-input.html
@@ -0,0 +1,10 @@
+<div class="td-search td-search--offline">
+  <div class="td-search__icon"></div>
+  <input
+    type="search"
+    class="td-search__input form-control"
+    placeholder="{{ T "ui_search" }}"
+    aria-label="{{ T "ui_search" }}"
+    autocomplete="off"
+  >
+</div>