Greasemonkey / Tampermonkey script to bring back hoverable alt text in Mastodon 4.4

mastodon_reinstate_title_text.user.js

// ==UserScript==
// @name         Mastodon 4.4 - Reinstate title text!
// @namespace    http://tampermonkey.net/
// @version      2025-07-22
// @description  Restores alt text in the title attribute of images and videos, allowing the alt text to be viewed in a tooltip while hovering with the mouse. See https://github.com/mastodon/mastodon/issues/33799
// @author       Graham Sutherland
// @match        https://chaos.social/*
// @icon         https://mastodon.social/favicon.ico
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    new MutationObserver(mutationList => {
        mutationList.forEach(mutation => {
            // watch for new 'img' and 'video' elements
            Array.from(mutation.addedNodes)
                .filter(el => el.nodeName != '#text')
                .flatMap(el => [
                    (el.tagName == 'IMG' || el.tagName == 'VIDEO') ? [ el ] : [],
                    Array.from(el.getElementsByTagName('IMG')),
                    Array.from(el.getElementsByTagName('VIDEO'))
                ])
                .flat()
                .forEach(el =>
            {
                // if this media element has alt text, but no title text (missing attribute or empty string), clone alt text into the title attribute
                if (el.hasAttribute("alt"))
                {
                    if (!el.hasAttribute("title") || el.getAttribute("title") == "")
                    {
                        el.setAttribute("title", el.getAttribute("alt"));
                    }
                }
            });
        });
    }).observe(document.body, { childList: true, subtree: true });
})();