Enjoy a smoother, truly live Twitch experience! This script intelligently manages playback speed to eliminate frustrating lag, keeping you in the moment. Comes with a simple on-screen menu to customize your settings.
// ==UserScript==
// @name Twitch Low-Latency Catch-Up
// @version 1.1
// @description Enjoy a smoother, truly live Twitch experience! This script intelligently manages playback speed to eliminate frustrating lag, keeping you in the moment. Comes with a simple on-screen menu to customize your settings.
// @author Mattskiiau
// @license GNU GPLv3
// @match https://www.twitch.tv/*
// @match https://player.twitch.tv/*
// @grant none
// @run-at document-start
// @namespace https://greasyfork.org/users/1519406
// ==/UserScript==
(function () {
'use strict';
const DEFAULTS = {
targetLag: 2.5,
maxBoost: 1.03,
enabled: true,
checkMs: 100,
rateEpsilon: 0.003,
bufferSafety: 1.5,
rateStepUp: 0.05,
rateStepDown: 0.05,
rateSmoothFactor: 0.55,
rateMinStep: 0.01,
normalizeLag: 1.25, // This will be auto-calculated
};
let SETTINGS = { ...DEFAULTS };
const LS_KEYS = ['llc-v3.0-settings', 'llc-v2.0-settings', 'llc-v1.9-settings', 'llc-v1.8-settings', 'llc-v1.7-settings', 'llc-v1.6-settings', 'llc-v1.5-settings', 'llc-v1.4-settings','llc-v1.3-settings','llc-v1.2-settings','llc-v1.1'];
const UI_KEYS = ['llc-v3.0-ui', 'llc-v2.0-ui', 'llc-v1.9-ui', 'llc-v1.8-ui', 'llc-v1.7-ui', 'llc-v1.6-ui', 'llc-v1.5-ui', 'llc-v1.4-ui','llc-v1.3-ui','llc-v1.2-ui'];
const PANEL_ID = 'llc30';
const VIDEO_SCAN_INTERVAL = 2000;
let activeVideo = null;
let cachedVideos = [];
let lastVideoScan = 0;
const panelRefs = { root: null, body: null, lag: null, rate: null, minBtn: null };
let rateEstimate = 1;
function resetPanelRefs() {
panelRefs.root = panelRefs.body = panelRefs.lag = panelRefs.rate = panelRefs.minBtn = null;
}
function load() {
let loadedSettings = null;
for (const k of LS_KEYS) {
try {
const s = JSON.parse(localStorage.getItem(k) || 'null');
if (s && typeof s === 'object') {
loadedSettings = s;
break;
}
} catch (_) {}
}
if (loadedSettings) {
SETTINGS = Object.assign({}, DEFAULTS, loadedSettings);
}
}
function save() {
try {
localStorage.setItem(LS_KEYS[0], JSON.stringify(SETTINGS));
} catch (_) {}
}
function loadUI() {
for (const k of UI_KEYS) {
try {
const v = JSON.parse(localStorage.getItem(k) || 'null');
if (v) return v;
} catch (_) {}
}
return {};
}
function saveUIState(obj) {
try {
localStorage.setItem(UI_KEYS[0], JSON.stringify(obj));
} catch (_) {}
}
function log(...a) {
if (SETTINGS.debug) console.log('[LLC]', ...a);
}
function collectVideos(root) {
const out = [];
try {
const walker = document.createTreeWalker(root || document, NodeFilter.SHOW_ELEMENT);
let n = walker.currentNode;
while (n) {
if (n.tagName === 'VIDEO') out.push(n);
if (n.shadowRoot) out.push(...collectVideos(n.shadowRoot));
if (n.tagName === 'IFRAME') {
try {
if (n.contentDocument) out.push(...collectVideos(n.contentDocument));
} catch (_) {}
}
n = walker.nextNode();
}
} catch (_) {}
return out;
}
function isRectVisible(rect) {
return rect.width > 0 && rect.height > 0 && rect.bottom > 0 && rect.right > 0 && rect.left < innerWidth && rect.top < innerHeight;
}
function isCandidate(video) {
return !!video && video.isConnected && video.readyState >= 2;
}
function refreshVideos(force = false) {
const now = Date.now();
if (!force && now - lastVideoScan < VIDEO_SCAN_INTERVAL) {
cachedVideos = cachedVideos.filter(isCandidate);
if (!cachedVideos.includes(activeVideo)) activeVideo = null;
if (cachedVideos.length) return cachedVideos;
}
lastVideoScan = now;
cachedVideos = collectVideos(document).filter(isCandidate);
if (!cachedVideos.includes(activeVideo)) activeVideo = null;
return cachedVideos;
}
function selectBestVideo(list) {
let best = null;
let bestScore = -1;
for (const v of list) {
const rect = v.getBoundingClientRect();
if (!isRectVisible(rect)) continue;
const score = rect.width * rect.height;
if (score > bestScore) {
bestScore = score;
best = v;
}
}
return best;
}
function pickActiveVideo() {
if (isCandidate(activeVideo)) {
const rect = activeVideo.getBoundingClientRect();
if (isRectVisible(rect)) return activeVideo;
activeVideo = null;
}
let vids = refreshVideos(false);
let best = selectBestVideo(vids);
if (!best) {
vids = refreshVideos(true);
best = selectBestVideo(vids);
}
if (best) activeVideo = best;
return best;
}
function isAdPlaying() {
return !!(document.querySelector('[data-a-target="video-ad-label"]') || document.querySelector('.ad-banner, .player-ad-banner, .video-player__ad-overlay'));
}
function isLive(video) {
if (!video) return false;
const liveish = !Number.isFinite(video.duration) || (video.seekable && video.seekable.length > 0);
return liveish;
}
function extractLag(range, currentTime) {
try {
if (range && range.length) {
const end = range.end(range.length - 1);
const lag = end - currentTime;
if (Number.isFinite(lag) && lag >= -1 && lag < 120) return lag;
}
} catch (_) {}
return NaN;
}
function getLag(video) {
const lagFromSeekable = extractLag(video.seekable, video.currentTime);
if (Number.isFinite(lagFromSeekable)) return lagFromSeekable;
return extractLag(video.buffered, video.currentTime);
}
function getBufferedAhead(video) {
try {
const bf = video && video.buffered;
if (bf && bf.length) {
return Math.max(0, bf.end(bf.length - 1) - video.currentTime);
}
} catch (_) {}
return 0;
}
function clamp(v, min, max) {
return Math.max(min, Math.min(max, v));
}
function setRate(video, rate) {
if (!video) return 1;
const target = clamp(rate, 0.25, SETTINGS.maxBoost);
if (Math.abs(video.playbackRate - target) > SETTINGS.rateEpsilon) {
try {
video.playbackRate = target;
} catch (_) {}
try {
if ('preservesPitch' in video) video.preservesPitch = true;
if ('mozPreservesPitch' in video) video.mozPreservesPitch = true;
if ('webkitPreservesPitch' in video) video.webkitPreservesPitch = true;
} catch (_) {}
log('rate:', target.toFixed(2));
}
rateEstimate = video.playbackRate;
return video.playbackRate;
}
const originalPlaybackRate = Object.getOwnPropertyDescriptor(HTMLMediaElement.prototype, 'playbackRate');
if (originalPlaybackRate) {
Object.defineProperty(HTMLMediaElement.prototype, 'playbackRate', {
get() {
return originalPlaybackRate.get.call(this);
},
set(v) {
try {
originalPlaybackRate.set.call(this, v);
} catch (_) {}
},
});
}
function smoothRate(desired) {
const current = rateEstimate;
if (!Number.isFinite(desired)) return current;
const delta = desired - current;
if (Math.abs(delta) < SETTINGS.rateMinStep) {
rateEstimate = clamp(desired, 0.25, SETTINGS.maxBoost);
return rateEstimate;
}
const limit = delta > 0 ? SETTINGS.rateStepUp : SETTINGS.rateStepDown;
const step = Math.min(Math.abs(delta) * SETTINGS.rateSmoothFactor, limit);
const next = current + Math.sign(delta) * step;
rateEstimate = clamp(next, 0.25, SETTINGS.maxBoost);
return rateEstimate;
}
function updatePanelDisplay(lag, rate) {
if (!SETTINGS.enabled) {
if (panelRefs.lag) panelRefs.lag.textContent = 'off';
if (panelRefs.rate) panelRefs.rate.textContent = '1.00×';
return;
}
if (panelRefs.lag) panelRefs.lag.textContent = Number.isFinite(lag) ? `${lag.toFixed(1)} s` : '-- s';
if (panelRefs.rate) panelRefs.rate.textContent = (Number.isFinite(rate) ? rate : 1).toFixed(2) + '×';
}
function panel() {
if (panelRefs.root && panelRefs.root.isConnected) return;
if (!document.body) return;
const el = document.createElement('div');
el.id = PANEL_ID;
el.style.cssText = 'position:fixed;z-index:2147483647;background:#111c;color:#eee;border-radius:8px;font:12px system-ui,Segoe UI,Roboto,Arial;backdrop-filter:blur(4px);box-shadow:0 2px 10px rgba(0,0,0,.4);user-select:none;width:240px;';
const uiState = Object.assign({ left: null, top: null, collapsed: false, advanced: false }, loadUI());
el.innerHTML = `
<div id="llc_hdr" style="display:flex;align-items:center;gap:8px;padding:6px 8px;cursor:move">
<strong style="font-weight:600">Stats:</strong>
<span id="llc_l" style="opacity:.9">-- s</span>
<span id="llc_r" style="opacity:.9">1.00×</span>
<div style="flex:1"></div>
<button id="llc_min" title="Minimize" style="background:#222;color:#eee;border:0;border-radius:6px;padding:2px 6px;cursor:pointer">–</button>
</div>
<div id="llc_body" style="display: flex; flex-direction: column; gap: 8px; padding: 8px;">
<label style="display:flex; justify-content: space-between; align-items: center;">
<span>Target Delay:</span>
<span style="display: flex; align-items: center; gap: 4px;">
<input data-key="targetLag" type="number" step="0.1" min="0" style="width: 60px; text-align: right; border-radius: 4px; border: 1px solid #555; background: #222; color: #eee;">
<span style="width: 20px; text-align: left;">s</span>
</span>
</label>
<label style="display:flex; justify-content: space-between; align-items: center;">
<span>Speed Rate: </span>
<span style="display: flex; align-items: center; gap: 4px;">
<input data-key="maxBoost" type="number" step="0.01" min="1" max="5" style="width: 60px; text-align: right; border-radius: 4px; border: 1px solid #555; background: #222; color: #eee;">
<span style="width: 20px; text-align: left;">×</span>
</span>
</label>
<label style="display:flex; justify-content: space-between; align-items: center;">
<span>Enabled:</span>
<input data-key="enabled" type="checkbox">
</label>
</div>
<div id="llc_advanced_body" style="display: none; flex-direction: column; gap: 8px; padding: 8px; border-top: 1px solid #444;">
</div>
<div id="llc_footer" style="display:flex; justify-content: space-between; padding: 4px 8px 8px 8px;">
<button id="llc_advanced_toggle" style="background:none; border:none; color:#aaa; cursor:pointer;">Advanced ▾</button>
<button id="llc_reset" style="background:none; border:none; color:#aaa; cursor:pointer;">Reset</button>
</div>
`;
document.body.appendChild(el);
const hdr = el.querySelector('#llc_hdr');
const body = el.querySelector('#llc_body');
const advancedBody = el.querySelector('#llc_advanced_body');
const advancedToggleBtn = el.querySelector('#llc_advanced_toggle');
const resetBtn = el.querySelector('#llc_reset');
const footer = el.querySelector('#llc_footer');
const minBtn = el.querySelector('#llc_min');
panelRefs.root = el;
panelRefs.body = body;
panelRefs.lag = el.querySelector('#llc_l');
panelRefs.rate = el.querySelector('#llc_r');
panelRefs.minBtn = minBtn;
const inputs = {};
let advancedOpen = uiState.advanced;
const advancedSettings = {
checkMs: { min: 50, max: 5000, step: 50, unit: 'ms', title: 'How often the script checks for lag.' },
rateStepUp: { min: 0.01, max: 1, step: 0.01, unit: 'Δ/s', title: 'Maximum rate increase per second.' },
rateStepDown: { min: 0.01, max: 1, step: 0.01, unit: 'Δ/s', title: 'Maximum rate decrease per second.' },
rateSmoothFactor: { min: 0.01, max: 1, step: 0.01, unit: '', title: 'Smoothing factor for rate changes.' },
bufferSafety: { min: 0, max: 10, step: 0.1, unit: 's', title: 'Minimum video buffer required for max boost.' },
};
for (const [key, props] of Object.entries(advancedSettings)) {
const label = document.createElement('label');
label.style.cssText = 'display:flex; justify-content: space-between; align-items: center;';
label.innerHTML = `
<span style="display: flex; align-items: center; gap: 4px;">
${key.replace(/([A-Z])/g, ' $1').replace(/^./, str => str.toUpperCase())}
<span title="${props.title}" style="cursor:help; border: 1px solid #777; border-radius: 50%; width: 14px; height: 14px; display: inline-flex; justify-content: center; align-items: center; font-size: 10px;">i</span>
</span>
<span style="display: flex; align-items: center; gap: 4px;">
<input data-key="${key}" type="number" step="${props.step}" min="${props.min}" max="${props.max}" style="width: 60px; text-align: right; border-radius: 4px; border: 1px solid #555; background: #222; color: #eee;">
<span style="width: 20px; text-align: left;">${props.unit}</span>
</span>
`;
advancedBody.appendChild(label);
}
el.querySelectorAll('[data-key]').forEach(input => {
const key = input.dataset.key;
inputs[key] = input;
});
function updateUIFromSettings() {
for (const [key, input] of Object.entries(inputs)) {
if (input.type === 'checkbox') {
input.checked = SETTINGS[key];
} else {
input.value = SETTINGS[key];
}
}
}
function persist() {
for (const [key, input] of Object.entries(inputs)) {
const value = input.type === 'checkbox' ? input.checked : Number(input.value);
if (SETTINGS[key] !== value) {
SETTINGS[key] = value;
}
}
SETTINGS.normalizeLag = SETTINGS.targetLag / 2;
save();
}
el.querySelectorAll('[data-key]').forEach(input => {
input.addEventListener('input', persist);
});
resetBtn.addEventListener('click', () => {
SETTINGS = { ...DEFAULTS };
save();
updateUIFromSettings();
});
function setAdvancedVisible(visible) {
const collapsed = body.style.display === 'none';
advancedOpen = visible;
advancedBody.style.display = (!collapsed && visible) ? 'flex' : 'none';
advancedToggleBtn.textContent = visible ? 'Advanced ▴' : 'Advanced ▾';
saveUIState({ ...loadUI(), advanced: visible });
}
advancedToggleBtn.addEventListener('click', () => setAdvancedVisible(!advancedOpen));
function setCollapsed(collapsed) {
body.style.display = collapsed ? 'none' : 'flex';
advancedBody.style.display = (!collapsed && advancedOpen) ? 'flex' : 'none';
advancedToggleBtn.textContent = advancedOpen ? 'Advanced ▴' : 'Advanced ▾';
footer.style.display = collapsed ? 'none' : 'flex';
minBtn.textContent = collapsed ? '+' : '–';
saveUIState({ ...loadUI(), collapsed });
}
function toggleCollapsed() {
setCollapsed(body.style.display !== 'none');
}
minBtn.addEventListener('click', toggleCollapsed);
function placeInitial() {
const rect = el.getBoundingClientRect();
if (uiState.left == null || uiState.top == null) {
const left = clamp(innerWidth - rect.width - 12, 0, Math.max(0, innerWidth - rect.width));
const top = clamp(innerHeight - rect.height - 12, 0, Math.max(0, innerHeight - rect.height));
el.style.left = left + 'px';
el.style.top = top + 'px';
} else {
el.style.left = clamp(uiState.left, 0, innerWidth - rect.width) + 'px';
el.style.top = clamp(uiState.top, 0, innerHeight - rect.height) + 'px';
}
}
(function enableDrag() {
let dragging = false;
let ox = 0;
let oy = 0;
let sx = 0;
let sy = 0;
let moved = false;
hdr.addEventListener('pointerdown', (ev) => {
dragging = true;
moved = false;
hdr.setPointerCapture(ev.pointerId);
const r = el.getBoundingClientRect();
ox = ev.clientX;
oy = ev.clientY;
sx = r.left;
sy = r.top;
});
hdr.addEventListener('pointermove', (ev) => {
if (!dragging) return;
const dx = ev.clientX - ox;
const dy = ev.clientY - oy;
if (Math.abs(dx) > 3 || Math.abs(dy) > 3) moved = true;
const nx = clamp(sx + dx, 0, innerWidth - el.offsetWidth);
const ny = clamp(sy + dy, 0, innerHeight - el.offsetHeight);
el.style.left = nx + 'px';
el.style.top = ny + 'px';
});
hdr.addEventListener('pointerup', (ev) => {
if (!dragging) return;
dragging = false;
hdr.releasePointerCapture(ev.pointerId);
const r = el.getBoundingClientRect();
saveUIState({ left: r.left, top: r.top, collapsed: body.style.display === 'none' });
if (!moved) toggleCollapsed();
});
window.addEventListener('resize', () => {
const r = el.getBoundingClientRect();
el.style.left = clamp(r.left, 0, innerWidth - el.offsetWidth) + 'px';
el.style.top = clamp(r.top, 0, innerHeight - el.offsetHeight) + 'px';
});
})();
updateUIFromSettings();
setAdvancedVisible(uiState.advanced);
setCollapsed(uiState.collapsed);
placeInitial();
}
function controlLoop() {
const video = pickActiveVideo();
if (!video) {
updatePanelDisplay(NaN, 1);
return;
}
if (Number.isFinite(video.playbackRate)) {
rateEstimate = video.playbackRate;
}
if (!SETTINGS.enabled) {
rateEstimate = 1;
const applied = setRate(video, 1.0);
updatePanelDisplay(NaN, applied);
return;
}
if (!isLive(video) || isAdPlaying()) {
rateEstimate = 1;
const applied = setRate(video, 1.0);
updatePanelDisplay(NaN, applied);
return;
}
const lag = getLag(video);
if (!Number.isFinite(lag)) {
rateEstimate = 1;
const applied = setRate(video, 1.0);
updatePanelDisplay(NaN, applied);
return;
}
const bufferAhead = getBufferedAhead(video);
let targetRate = 1.0;
if (rateEstimate > 1.0) {
if (lag > SETTINGS.normalizeLag) {
const excess = lag - SETTINGS.normalizeLag;
const catchupSpan = Math.max(0.25, (SETTINGS.targetLag - SETTINGS.normalizeLag) * 1.5);
const normalized = clamp(excess / catchupSpan, 0, 1);
targetRate = 1 + normalized * (SETTINGS.maxBoost - 1);
} else {
targetRate = 1.0;
}
} else {
if (lag > SETTINGS.targetLag) {
const excess = lag - SETTINGS.targetLag;
const catchupSpan = Math.max(0.25, SETTINGS.targetLag * 1.5);
const normalized = clamp(excess / catchupSpan, 0, 1);
targetRate = 1 + normalized * (SETTINGS.maxBoost - 1);
}
}
if (targetRate > 1.0 && bufferAhead < SETTINGS.bufferSafety) {
const bufferScale = clamp(bufferAhead / SETTINGS.bufferSafety, 0, 1);
const maxAllowed = 1 + (SETTINGS.maxBoost - 1) * bufferScale;
targetRate = Math.min(targetRate, maxAllowed);
}
const smoothed = smoothRate(targetRate);
const applied = setRate(video, smoothed);
updatePanelDisplay(lag, applied);
}
function main() {
load();
if (document.readyState === 'loading') {
document.addEventListener('DOMContentLoaded', panel, { once: true });
} else {
panel();
}
setInterval(controlLoop, SETTINGS.checkMs);
}
main();
})();