diff --git a/templates/switchers.js b/templates/switchers.js
index 999ca10..cd4cbc2 100644
--- a/templates/switchers.js
+++ b/templates/switchers.js
@@ -1,197 +1,199 @@
-(function() {
-  'use strict';
-
-  if (!String.prototype.startsWith) {
-    Object.defineProperty(String.prototype, 'startsWith', {
-      value: function(search, rawPos) {
-        const pos = rawPos > 0 ? rawPos|0 : 0;
-        return this.substring(pos, pos + search.length) === search;
-      }
-    });
+'use strict';
+
+// File URIs must begin with either one or three forward slashes
+const _is_file_uri = (uri) => uri.startsWith('file:/');
+
+const _IS_LOCAL = _is_file_uri(window.location.href);
+const _CURRENT_RELEASE = DOCUMENTATION_OPTIONS.VERSION || '';
+const _CURRENT_VERSION = _CURRENT_RELEASE.split('.', 2).join('.');
+const _CURRENT_LANGUAGE = DOCUMENTATION_OPTIONS.LANGUAGE?.toLowerCase() || 'en';
+const _CURRENT_PREFIX = (() => {
+  if (_IS_LOCAL) return null;
+  // Sphinx 7.2+ defines the content root data attribute in the HTML element.
+  const _CONTENT_ROOT = document.documentElement.dataset.content_root;
+  if (_CONTENT_ROOT !== undefined) {
+    return new URL(_CONTENT_ROOT, window.location).pathname;
   }
+  // Fallback for older versions of Sphinx (used in Python 3.10 and older).
+  const _NUM_PREFIX_PARTS = _CURRENT_LANGUAGE === 'en' ? 2 : 3;
+  return window.location.pathname.split('/', _NUM_PREFIX_PARTS).join('/') + '/';
+})();
 
-  // Parses versions in URL segments like:
-  // "3", "dev", "release/2.7" or "3.6rc2"
-  const version_regexs = [
-    '(?:\\d)',
-    '(?:\\d\\.\\d[\\w\\d\\.]*)',
-    '(?:dev)',
-    '(?:release/\\d.\\d[\\x\\d\\.]*)'];
-
-  const all_versions = $VERSIONS;
-  const all_languages = $LANGUAGES;
-
-  function quote_attr(str) {
-      return '"' + str.replace('"', '\\"') + '"';
+const _ALL_VERSIONS = new Map(Object.entries($VERSIONS));
+const _ALL_LANGUAGES = new Map(Object.entries($LANGUAGES));
+
+/**
+ * @param {Map<string, string>} versions
+ * @returns {HTMLSelectElement}
+ * @private
+ */
+const _create_version_select = (versions) => {
+  const select = document.createElement('select');
+  select.className = 'version-select';
+  if (_IS_LOCAL) {
+    select.disabled = true;
+    select.title = 'Version switching is disabled in local builds';
   }
 
-  function build_version_select(release) {
-    let buf = ['<select id="version_select" aria-label="Python version">'];
-    const major_minor = release.split(".").slice(0, 2).join(".");
-
-    Object.entries(all_versions).forEach(function([version, title]) {
-      if (version === major_minor) {
-        buf.push('<option value=' + quote_attr(version) + ' selected="selected">' + release + '</option>');
-      } else {
-        buf.push('<option value=' + quote_attr(version) + '>' + title + '</option>');
-      }
-    });
+  for (const [version, title] of versions) {
+    const option = document.createElement('option');
+    option.value = version;
+    if (version === _CURRENT_VERSION) {
+      option.text = _CURRENT_RELEASE;
+      option.selected = true;
+    } else {
+      option.text = title;
+    }
+    select.add(option);
+  }
 
-    buf.push('</select>');
-    return buf.join('');
+  return select;
+};
+
+/**
+ * @param {Map<string, string>} languages
+ * @returns {HTMLSelectElement}
+ * @private
+ */
+const _create_language_select = (languages) => {
+  if (!languages.has(_CURRENT_LANGUAGE)) {
+    // In case we are browsing a language that is not yet in languages.
+    languages.set(_CURRENT_LANGUAGE, _CURRENT_LANGUAGE);
   }
 
-  function build_language_select(current_language) {
-    let buf = ['<select id="language_select" aria-label="Language">'];
+  const select = document.createElement('select');
+  select.className = 'language-select';
+  if (_IS_LOCAL) {
+    select.disabled = true;
+    select.title = 'Language switching is disabled in local builds';
+  }
 
-    Object.entries(all_languages).forEach(function([language, title]) {
-      if (language === current_language) {
-        buf.push('<option value="' + language + '" selected="selected">' + title + '</option>');
-      } else {
-        buf.push('<option value="' + language + '">' + title + '</option>');
-      }
-    });
-    if (!(current_language in all_languages)) {
-        // In case we're browsing a language that is not yet in all_languages.
-        buf.push('<option value="' + current_language + '" selected="selected">' +
-                 current_language + '</option>');
-        all_languages[current_language] = current_language;
-    }
-    buf.push('</select>');
-    return buf.join('');
+  for (const [language, title] of languages) {
+    const option = document.createElement('option');
+    option.value = language;
+    option.text = title;
+    if (language === _CURRENT_LANGUAGE) option.selected = true;
+    select.add(option);
   }
 
-  function navigate_to_first_existing(urls) {
-    // Navigate to the first existing URL in urls.
-    const url = urls.shift();
-    if (urls.length == 0 || url.startsWith("file:///")) {
-      window.location.href = url;
-      return;
-    }
+  return select;
+};
+
+/**
+ * Change the current page to the first existing URL in the list.
+ * @param {Array<string>} urls
+ * @private
+ */
+const _navigate_to_first_existing = (urls) => {
+  // Navigate to the first existing URL in urls.
+  for (const url of urls) {
     fetch(url)
-      .then(function(response) {
+      .then((response) => {
         if (response.ok) {
           window.location.href = url;
-        } else {
-          navigate_to_first_existing(urls);
+          return url;
         }
       })
-      .catch(function(error) {
-        navigate_to_first_existing(urls);
+      .catch((err) => {
+        console.error(`Error when fetching '${url}'!`);
+        console.error(err);
       });
   }
 
-  function on_version_switch() {
-    const selected_version = this.options[this.selectedIndex].value + '/';
-    const url = window.location.href;
-    const current_language = language_segment_from_url();
-    const current_version = version_segment_from_url();
-    const new_url = url.replace('/' + current_language + current_version,
-                                '/' + current_language + selected_version);
-    if (new_url != url) {
-      navigate_to_first_existing([
-        new_url,
-        url.replace('/' + current_language + current_version,
-                    '/' + selected_version),
-        '/' + current_language + selected_version,
-        '/' + selected_version,
-        '/'
-      ]);
-    }
-  }
-
-  function on_language_switch() {
-    let selected_language = this.options[this.selectedIndex].value + '/';
-    const url = window.location.href;
-    const current_language = language_segment_from_url();
-    const current_version = version_segment_from_url();
-    if (selected_language == 'en/') // Special 'default' case for English.
-      selected_language = '';
-    let new_url = url.replace('/' + current_language + current_version,
-                              '/' + selected_language + current_version);
-    if (new_url != url) {
-      navigate_to_first_existing([
-        new_url,
-        '/'
-      ]);
-    }
+  // if all else fails, redirect to the d.p.o root
+  window.location.href = '/';
+  return '/';
+};
+
+/**
+ * Callback for the version switcher.
+ * @param {Event} event
+ * @returns {void}
+ * @private
+ */
+const _on_version_switch = (event) => {
+  if (_IS_LOCAL) return;
+
+  const selected_version = event.target.value;
+  // English has no language prefix.
+  const new_prefix_en = `/${selected_version}/`;
+  const new_prefix =
+    _CURRENT_LANGUAGE === 'en'
+      ? new_prefix_en
+      : `/${_CURRENT_LANGUAGE}/${selected_version}/`;
+  if (_CURRENT_PREFIX !== new_prefix) {
+    // Try the following pages in order:
+    // 1. The current page in the current language with the new version
+    // 2. The current page in English with the new version
+    // 3. The documentation home in the current language with the new version
+    // 4. The documentation home in English with the new version
+    _navigate_to_first_existing([
+      window.location.href.replace(_CURRENT_PREFIX, new_prefix),
+      window.location.href.replace(_CURRENT_PREFIX, new_prefix_en),
+      new_prefix,
+      new_prefix_en,
+    ]);
   }
-
-  // Returns the path segment of the language as a string, like 'fr/'
-  // or '' if not found.
-  function language_segment_from_url() {
-    const path = window.location.pathname;
-    const language_regexp = '/((?:' + Object.keys(all_languages).join("|") + ')/)'
-    const match = path.match(language_regexp);
-    if (match !== null)
-      return match[1];
-    return '';
+};
+
+/**
+ * Callback for the language switcher.
+ * @param {Event} event
+ * @returns {void}
+ * @private
+ */
+const _on_language_switch = (event) => {
+  if (_IS_LOCAL) return;
+
+  const selected_language = event.target.value;
+  // English has no language prefix.
+  const new_prefix =
+    selected_language === 'en'
+      ? `/${_CURRENT_VERSION}/`
+      : `/${selected_language}/${_CURRENT_VERSION}/`;
+  if (_CURRENT_PREFIX !== new_prefix) {
+    // Try the following pages in order:
+    // 1. The current page in the new language with the current version
+    // 2. The documentation home in the new language with the current version
+    _navigate_to_first_existing([
+      window.location.href.replace(_CURRENT_PREFIX, new_prefix),
+      new_prefix,
+    ]);
   }
-
-  // Returns the path segment of the version as a string, like '3.6/'
-  // or '' if not found.
-  function version_segment_from_url() {
-    const path = window.location.pathname;
-    const language_segment = language_segment_from_url();
-    const version_segment = '(?:(?:' + version_regexs.join('|') + ')/)';
-    const version_regexp = language_segment + '(' + version_segment + ')';
-    const match = path.match(version_regexp);
-    if (match !== null)
-      return match[1];
-    return ''
-  }
-
-  function create_placeholders_if_missing() {
-    const version_segment = version_segment_from_url();
-    const language_segment = language_segment_from_url();
-    const index = "/" + language_segment + version_segment;
-
-    if (document.querySelectorAll('.version_switcher_placeholder').length > 0) {
-      return;
-    }
-
-    const html = '<span class="language_switcher_placeholder"></span> \
-<span class="version_switcher_placeholder"></span> \
-<a href="/" id="indexlink">Documentation</a> &#187;';
-
-    const probable_places = [
-      "body>div.related>ul>li:not(.right):contains('Documentation'):first",
-      "body>div.related>ul>li:not(.right):contains('documentation'):first",
-    ];
-
-    for (let i = 0; i < probable_places.length; i++) {
-      let probable_place = $(probable_places[i]);
-      if (probable_place.length == 1) {
-        probable_place.html(html);
-        document.getElementById('indexlink').href = index;
-        return;
-      }
-    }
-  }
-
-  document.addEventListener('DOMContentLoaded', function() {
-    const language_segment = language_segment_from_url();
-    const current_language = language_segment.replace(/\/+$/g, '') || 'en';
-    const version_select = build_version_select(DOCUMENTATION_OPTIONS.VERSION);
-
-    create_placeholders_if_missing();
-
-    let placeholders = document.querySelectorAll('.version_switcher_placeholder');
-    placeholders.forEach(function(placeholder) {
-      placeholder.innerHTML = version_select;
-
-      let selectElement = placeholder.querySelector('select');
-      selectElement.addEventListener('change', on_version_switch);
+};
+
+/**
+ * Initialisation function for the version and language switchers.
+ * @returns {void}
+ * @private
+ */
+const _initialise_switchers = () => {
+  const versions = _ALL_VERSIONS;
+  const languages = _ALL_LANGUAGES;
+
+  const version_select = _create_version_select(versions);
+  document
+    .querySelectorAll('.version_switcher_placeholder')
+    .forEach((placeholder) => {
+      const s = version_select.cloneNode(true);
+      s.addEventListener('change', _on_version_switch);
+      placeholder.append(s);
+      placeholder.classList.remove('version_switcher_placeholder');
     });
 
-    const language_select = build_language_select(current_language);
-
-    placeholders = document.querySelectorAll('.language_switcher_placeholder');
-    placeholders.forEach(function(placeholder) {
-      placeholder.innerHTML = language_select;
-
-      let selectElement = placeholder.querySelector('select');
-      selectElement.addEventListener('change', on_language_switch);
+  const language_select = _create_language_select(languages);
+  document
+    .querySelectorAll('.language_switcher_placeholder')
+    .forEach((placeholder) => {
+      const s = language_select.cloneNode(true);
+      s.addEventListener('change', _on_language_switch);
+      placeholder.append(s);
+      placeholder.classList.remove('language_switcher_placeholder');
     });
-  });
-})();
+};
+
+if (document.readyState !== 'loading') {
+  _initialise_switchers();
+} else {
+  document.addEventListener('DOMContentLoaded', _initialise_switchers);
+}