diff --git a/docs/website_files/version-picker.js b/docs/website_files/version-picker.js
new file mode 100644
index 0000000000..bb35a7d896
--- /dev/null
+++ b/docs/website_files/version-picker.js
@@ -0,0 +1,127 @@
+
+const dropdown = document.querySelector('.version-picker .dropdown');
+const dropdownMenu = dropdown.querySelector('.dropdown-menu');
+
+fetchVersions(dropdown, dropdownMenu).then(() => {
+ initializeVersionDropdown(dropdown, dropdownMenu);
+});
+
+/**
+ * Initialize the dropdown functionality for version selection.
+ *
+ * @param {Element} dropdown - The dropdown element.
+ * @param {Element} dropdownMenu - The dropdown menu element.
+ */
+function initializeVersionDropdown(dropdown, dropdownMenu) {
+ // Toggle the dropdown menu on click
+ dropdown.addEventListener('click', function () {
+ this.setAttribute('tabindex', 1);
+ this.classList.toggle('active');
+ dropdownMenu.style.display = (dropdownMenu.style.display === 'block') ? 'none' : 'block';
+ });
+
+ // Remove the 'active' class and hide the dropdown menu on focusout
+ dropdown.addEventListener('focusout', function () {
+ this.classList.remove('active');
+ dropdownMenu.style.display = 'none';
+ });
+
+ // Handle item selection within the dropdown menu
+ const dropdownMenuItems = dropdownMenu.querySelectorAll('li');
+ dropdownMenuItems.forEach(function (item) {
+ item.addEventListener('click', function () {
+ dropdownMenuItems.forEach(function (item) {
+ item.classList.remove('active');
+ });
+ this.classList.add('active');
+ dropdown.querySelector('span').textContent = this.textContent;
+ dropdown.querySelector('input').value = this.getAttribute('id');
+
+ window.location.href = changeVersion(window.location.href, this.textContent);
+ });
+ });
+};
+
+/**
+ * This function fetches the available versions from a GitHub repository
+ * and inserts them into the version picker.
+ *
+ * @param {Element} dropdown - The dropdown element.
+ * @param {Element} dropdownMenu - The dropdown menu element.
+ * @returns {Promise<Array<string>>} A promise that resolves with an array of available versions.
+ */
+function fetchVersions(dropdown, dropdownMenu) {
+ return new Promise((resolve, reject) => {
+ window.addEventListener("load", () => {
+
+ fetch("https://api.github.com/repos/matrix-org/synapse/git/trees/gh-pages", {
+ cache: "force-cache",
+ }).then(res =>
+ res.json()
+ ).then(resObject => {
+ const excluded = ['dev-docs', 'v1.91.0', 'v1.80.0', 'v1.69.0'];
+ const tree = resObject.tree.filter(item => item.type === "tree" && !excluded.includes(item.path));
+ const versions = tree.map(item => item.path).sort(sortVersions);
+
+ // Create a list of <li> items for versions
+ versions.forEach((version) => {
+ const li = document.createElement("li");
+ li.textContent = version;
+ li.id = version;
+
+ if (window.SYNAPSE_VERSION === version) {
+ li.classList.add('active');
+ dropdown.querySelector('span').textContent = version;
+ dropdown.querySelector('input').value = version;
+ }
+
+ dropdownMenu.appendChild(li);
+ });
+
+ resolve(versions);
+
+ }).catch(ex => {
+ console.error("Failed to fetch version data", ex);
+ reject(ex);
+ })
+ });
+ });
+}
+
+/**
+ * Custom sorting function to sort an array of version strings.
+ *
+ * @param {string} a - The first version string to compare.
+ * @param {string} b - The second version string to compare.
+ * @returns {number} - A negative number if a should come before b, a positive number if b should come before a, or 0 if they are equal.
+ */
+function sortVersions(a, b) {
+ // Put 'develop' and 'latest' at the top
+ if (a === 'develop' || a === 'latest') return -1;
+ if (b === 'develop' || b === 'latest') return 1;
+
+ const versionA = (a.match(/v\d+(\.\d+)+/) || [])[0];
+ const versionB = (b.match(/v\d+(\.\d+)+/) || [])[0];
+
+ return versionB.localeCompare(versionA);
+}
+
+/**
+ * Change the version in a URL path.
+ *
+ * @param {string} url - The original URL to be modified.
+ * @param {string} newVersion - The new version to replace the existing version in the URL.
+ * @returns {string} The updated URL with the new version.
+ */
+function changeVersion(url, newVersion) {
+ const parsedURL = new URL(url);
+ const pathSegments = parsedURL.pathname.split('/');
+
+ // Modify the version
+ pathSegments[2] = newVersion;
+
+ // Reconstruct the URL
+ parsedURL.pathname = pathSegments.join('/');
+
+ return parsedURL.href;
+}
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