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Fixing YT SABR fresh session load issue #334

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Merged
ryanbr merged 2 commits into from
Jun 20, 2026
Merged

Fixing YT SABR fresh session load issue #334

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f4bc853
Fixing YT SABR fresh session load issue
griffinallen Jun 19, 2026
fdf1415
Fixing Youtube Premium check
griffinallen Jun 19, 2026
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2 changes: 1 addition & 1 deletion dist/resources.json
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101 changes: 59 additions & 42 deletions resources/brave-yt-sabr-fix.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,18 +5,18 @@
// backoff remains, causing a 4-16 second spinner.
// From: https://iter.ca/post/yt-adblock/
//
// Two-pronged fix:
// The fix intercepts SABR streaming responses and looks for a real backoff
// (backoffTimeMs in the protobuf). When one is found it does two things:
//
// 1. SPA navigation: When clicking between videos without a page reload,
// the player reuses the old SABR session (which may already have a
// backoff). On yt-navigate-finish, we set isInlinePlaybackNoAd on the
// player's video data (telling it there's no ad slot), then call
// cancelPlayback() + loadVideoById() to force a new SABR session.
// 1. Fresh ad-free session: if the backoff is blocking initial playback,
// set isInlinePlaybackNoAd on the player's video data (telling it there's
// no ad slot), then call cancelPlayback() + loadVideoById() to force a new
// SABR session with no ad slot. Guarded per video and only before playback
// starts, so no-ad videos and mid-playback pacing backoffs are left alone.
//
// 2. SABR response patching (full page loads): Intercept SABR streaming
// responses and rewrite backoffTimeMs in the protobuf. This handles
// page reloads and direct navigations where the SABR session was
// already established before the scriptlet could intervene.
// 2. Backoff patching: the backoffTimeMs value is rewritten regardless, as a
// fallback for when the fresh session still carries a backoff and to smooth
// the normal pacing backoffs that occur mid-playback.
//
// To use this scriptlet:
// 1. Go to brave://settings/shields/filters
Expand All @@ -33,39 +33,49 @@
const elapsed = () => ((Date.now() - startTime) / 1000).toFixed(2) + 's';
const log = (...args) => { if (DEBUG) console.log(LOG_PREFIX, elapsed(), ...args); };

// Premium accounts have no ads and no backoff, nothing to do.
if (document.querySelector('a#logo[title*="Premium" i]')) return;
// Premium accounts have no ads and no backoff, nothing to do. We can't check
// this up front: the scriptlet runs at document_start (so it can wrap fetch
// before YouTube grabs its own reference), but the masthead logo doesn't
// exist yet, so the selector would always miss. Instead resolve it lazily and
// memoize — by the time any SABR fetch fires the logo is present. Stays null
// (unknown) until the DOM can answer, so we never cache a premature "false".
let premiumCached = null;
function isPremium() {
if (premiumCached !== null) return premiumCached;
const logo = document.querySelector('a#logo[title]');
if (!logo) return false; // DOM not ready — don't cache this answer
premiumCached = /premium/i.test(logo.getAttribute('title') || '');
return premiumCached;
}

// Prong 1: On SPA navigation, force a new ad-free SABR session.
// Set isInlinePlaybackNoAd on the video data so the new session
// doesn't get an ad slot, then tear down the old session and start fresh.
// Initialize to the current vid so the initial yt-navigate-finish
// (which fires on page load completion, not just SPA nav) is treated
// as a duplicate and skipped. Avoids tearing down playback on refresh.
// We skip teardown when there's no prior session to clear.
let lastReloadedVid = new URL(window.location.href).searchParams.get('v') || '';
window.addEventListener('yt-navigate-finish', () => {
// Force a fresh ad-free SABR session. Called from the SABR interceptor
// below when it sees a real backoff. Set isInlinePlaybackNoAd so the new
// session gets no ad slot, then tear down the current session and reload.
// Guarded per video (one reload each, so a session that still backs off
// falls back to patching rather than looping) and skipped once playback has
// started — a no-ad video has no backoff, and a mid-playback backoff is
// normal pacing.
let reloadedVid = null;
function forceFreshSession() {
const vid = new URL(window.location.href).searchParams.get('v');
if (!vid || vid === lastReloadedVid) return;
const hadPriorSession = lastReloadedVid !== '';
lastReloadedVid = vid;
if (!hadPriorSession) return;

setTimeout(() => {
const player = document.querySelector('#movie_player');
if (!player?.cancelPlayback || !player?.loadVideoById) return;

// Set the no-ad flag before reloading so the new session picks it up
const vd = player.getVideoData?.();
if (vd) vd.isInlinePlaybackNoAd = true;

player.cancelPlayback();
player.loadVideoById(vid);
log('forced new SABR session for', vid);
}, 100);
});
if (!vid || vid === reloadedVid) return;
const video = document.querySelector('video');
if (video && video.currentTime > 1) return;
reloadedVid = vid;
const player = document.querySelector('#movie_player');
if (!player?.cancelPlayback || !player?.loadVideoById) return;

// Set the no-ad flag before reloading so the new session picks it up
const vd = player.getVideoData?.();
if (vd) vd.isInlinePlaybackNoAd = true;

player.cancelPlayback();
player.loadVideoById(vid);
log('forced fresh ad-free session for', vid);
}

// Prong 2: Intercept SABR responses and patch backoffTimeMs.
// Intercept SABR responses: detect a real backoff, force a fresh ad-free
// session if needed (see forceFreshSession above), and patch backoffTimeMs.
// Tee the body so media chunks (>=1000 bytes) pass through untouched
// — only the small control messages carrying the backoff field get
// buffered and re-emitted as a synthesized Response.
Expand All @@ -74,7 +84,9 @@
window.fetch = function(resource, init) {
const url = typeof resource === 'string' ? resource : (resource?.url || '');

if (url.includes('googlevideo.com') && url.includes('sabr=1')) {
// Premium has no ad backoff — skip the tee/scan entirely (re-checked
// cheaply per request; resolves once the masthead has rendered).
if (url.includes('googlevideo.com') && url.includes('sabr=1') && !isPremium()) {
let rn = '';
try { rn = new URL(url).searchParams.get('rn') || ''; } catch(e) {}
log('SABR fetch rn=' + rn);
Expand All @@ -96,7 +108,9 @@
return new Response(pass, reinit);
}
log('small response rn=' + rn, 'size=' + bytes.length);
patchBackoffField(bytes, rn);
// A real backoff blocks initial playback; force a fresh
// ad-free session (guarded per video, skipped mid-playback).
if (patchBackoffField(bytes, rn)) forceFreshSession();
const out = new Response(bytes, reinit);
try {
Object.defineProperty(out, 'url', { value: response.url, configurable: true });
Expand Down Expand Up @@ -142,6 +156,7 @@
// flag. We rewrite the varint in place, keeping the same byte count
// so the message structure stays valid.
function patchBackoffField(bytes, rn) {
let patched = false;
for (let i = 0; i < bytes.length - 2; i++) {
if (bytes[i] !== 0x20) continue;
let val = 0, shift = 0, end = i + 1;
Expand All @@ -160,8 +175,10 @@
remaining >>>= 7;
}
bytes[pos] = remaining & 0x7f;
patched = true;
}
}
return patched;
}

if (DEBUG) {
Expand Down
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