Show comments in the right sidebar with a Comments/Recommended toggle on YouTube watch pages.
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// ==UserScript==
// @name YouTube Comments Sidebar (Toggle, 2025)
// @namespace yt-comments-sidebar
// @version 1.3
// @description Show comments in the right sidebar with a Comments/Recommended toggle on YouTube watch pages.
// @match https://www.youtube.com/*
// @run-at document-start
// @grant none
// @license MIT
// ==/UserScript==
(function () {
"use strict";
const IS_WATCH = () => location.pathname === "/watch" && /[?&]v=/.test(location.search);
const QS = sel => document.querySelector(sel);
const SELECTORS = {
flexy: "ytd-watch-flexy",
secondary: "ytd-watch-flexy #secondary",
comments: "ytd-watch-flexy ytd-comments#comments, ytd-watch-flexy #comments",
};
const STYLE_ID = "tm-ycs-styles";
const WRAP_ID = "tm-ycs-wrap";
const TABS_ID = "tm-ycs-tabs";
const UP_NEXT_ID = "tm-ycs-upnext";
const COMMENTS_WRAP_ID = "tm-ycs-comments";
function injectStyles() {
if (QS(`#${STYLE_ID}`)) return;
const s = document.createElement("style");
s.id = STYLE_ID;
s.textContent = `
#${TABS_ID} {
display:flex; gap:.5rem; align-items:center;
position:sticky; top:56px; z-index:5;
padding:.5rem .75rem; border-bottom:1px solid rgba(255,255,255,.08);
background: rgba(18,18,18,.98);
backdrop-filter: saturate(120%) blur(6px);
}
#${TABS_ID} button{
font: 500 13px/1.2 system-ui, -apple-system, Segoe UI, Roboto, Arial;
padding:.4rem .7rem; border-radius:999px; border:1px solid transparent; cursor:pointer;
background:#272727; color:#eee;
}
#${TABS_ID} button.active{ background:#3a3a3a; border-color:#4a4a4a; }
#${COMMENTS_WRAP_ID}, #${UP_NEXT_ID} {
max-height: calc(100vh - 56px - 44px); /* header + tabs */
overflow-y: auto; overflow-x: hidden;
}
/* Make comments readable in the narrow column */
#${COMMENTS_WRAP_ID} #content { max-width: 100% !important; }
`;
document.documentElement.appendChild(s);
}
function waitFor(selector, { timeout = 15000, root = document } = {}) {
return new Promise((resolve, reject) => {
const found = root.querySelector(selector);
if (found) return resolve(found);
const obs = new MutationObserver(() => {
const el = root.querySelector(selector);
if (el) {
obs.disconnect();
resolve(el);
}
});
obs.observe(root, { childList: true, subtree: true });
setTimeout(() => {
obs.disconnect();
reject(new Error("Timeout waiting for " + selector));
}, timeout);
});
}
function buildTabs() {
const tabs = document.createElement("div");
tabs.id = TABS_ID;
const btnComments = document.createElement("button");
btnComments.textContent = "Comments";
btnComments.dataset.target = COMMENTS_WRAP_ID;
const btnUpNext = document.createElement("button");
btnUpNext.textContent = "Recommended";
btnUpNext.dataset.target = UP_NEXT_ID;
tabs.append(btnComments, btnUpNext);
function activate(targetId) {
const commentsWrap = QS(`#${COMMENTS_WRAP_ID}`);
const upnextWrap = QS(`#${UP_NEXT_ID}`);
if (!commentsWrap || !upnextWrap) return;
const buttons = tabs.querySelectorAll("button");
buttons.forEach(b => b.classList.toggle("active", b.dataset.target === targetId));
commentsWrap.style.display = (targetId === COMMENTS_WRAP_ID) ? "" : "none";
upnextWrap.style.display = (targetId === UP_NEXT_ID) ? "" : "none";
}
tabs.addEventListener("click", (e) => {
const b = e.target.closest("button");
if (!b) return;
activate(b.dataset.target);
});
// default to Comments first
queueMicrotask(() => activate(COMMENTS_WRAP_ID));
return tabs;
}
function wrapSecondary(secondary) {
if (QS(`#${WRAP_ID}`)) return; // already wrapped
// Move existing children into our UpNext wrapper
const upNext = document.createElement("div");
upNext.id = UP_NEXT_ID;
const frag = document.createDocumentFragment();
while (secondary.firstChild) frag.appendChild(secondary.firstChild);
upNext.appendChild(frag);
const commentsWrap = document.createElement("div");
commentsWrap.id = COMMENTS_WRAP_ID;
const container = document.createElement("div");
container.id = WRAP_ID;
const tabs = buildTabs();
container.append(tabs, commentsWrap, upNext);
secondary.appendChild(container);
}
function moveCommentsIntoSidebar() {
const comments = QS(SELECTORS.comments);
const slot = QS(`#${COMMENTS_WRAP_ID}`);
if (!comments || !slot) return false;
// Only move once
if (!slot.contains(comments)) {
slot.appendChild(comments);
}
return true;
}
function primeCommentsLoad() {
// If YouTube hasn’t hydrated comments yet, nudge it by briefly scrolling
// the original position into view (if it exists in DOM).
const original = QS(SELECTORS.comments);
if (original) {
original.scrollIntoView({ block: "center" });
}
}
async function initOnce() {
if (!IS_WATCH()) return;
injectStyles();
const flexy = await waitFor(SELECTORS.flexy).catch(() => null);
if (!flexy) return;
const secondary = await waitFor(SELECTORS.secondary, { root: flexy }).catch(() => null);
if (!secondary) return;
wrapSecondary(secondary);
primeCommentsLoad();
// Keep trying to capture comments as soon as they appear
let tries = 0;
const maxTries = 40;
const interval = setInterval(() => {
const ok = moveCommentsIntoSidebar();
tries++;
if (ok || tries >= maxTries) clearInterval(interval);
}, 500);
}
// Handle SPA navigation and first load
const boot = () => {
if (!IS_WATCH()) return;
initOnce().catch(() => {});
};
// YouTube fires this on in-page navigation
window.addEventListener("yt-navigate-finish", boot);
// Also run after full load
window.addEventListener("load", boot);
// And if URL changes without event (edge cases)
let lastHref = location.href;
new MutationObserver(() => {
if (location.href !== lastHref) {
lastHref = location.href;
boot();
}
}).observe(document, { childList: true, subtree: true });
})();