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For Bluetooth, 150-250 ms is typical. AAC headphones (AirPods, most phones) usually land near 150-220 ms; aptX/LDAC closer to 80-150 ms; aptX Low Latency or LE Audio 40-80 ms; cheap USB BT dongles or multipoint can need 300-400 ms. Start at 180 ms and adjust in 20-50 ms steps.

Walk through these in order: (1) the big toggle at the top of the popup must be on; (2) check Site Mode in Settings - Only listed / Exclude listed can keep LagSync out of the page; (3) reload the tab after enabling, since hooks install at document_start; (4) iframe players intentionally disable trim. If mode: none appears in stats view, the page exposes no pipeline LagSync can hook.

For increases, LagSync waits for already-buffered video to drain (or trims it, when allowed) before the new delayed segments reach the player. The countdown estimates when the new delay first becomes audible. Decreases and turning off are immediate. Trim-blocked sites (Netflix, Prime, no-DVR live, iframes) cannot shorten the wait.

Drop one step in Delay increase speed (Instant -> Fast -> Balanced -> Gentle), or raise Max buffer ahead to 10s/20s. Lock the player's quality during testing. On Prime, Instant mode is intentionally a single hard-jump and may briefly stall once. If hardware acceleration is off, frame capture (canvas) will be CPU-heavy.

Adaptive streams sometimes switch audio codecs (Opus/AAC on YouTube) or bitrates mid-playback, and the new track lines up slightly differently. Pin the player's quality in the gear menu so it does not re-pick mid-stream, or seek a few seconds back and forward to force the player to reinitialize. For Netflix, set a fixed quality in Account -> Playback settings.

You are on the canvas pipeline (Twitch live, YouTube no-DVR live, Firefox blob streams, or any page that fell back to frame capture). Canvas redraws every frame and is more expensive than MSE. Lower resolution, hide chat, close background tabs, and confirm browser hardware acceleration is on.

Yes. These are DRM and trim is blocked, so increases only kick in once the existing buffer drains. Start near 180 ms. On Prime, Auto-optimize sets Instant + 0s buffer. Set a fixed streaming quality in account settings and reload the player after changing extension settings.

YouTube live with DVR behaves like VOD (MSE, trim allowed). No-DVR live uses canvas (higher CPU, trim blocked). Twitch and Kick are blob-backed live: worker-MSE on Chrome, canvas on Edge/Firefox by design. Use a 200-250 ms baseline for live and lock quality.

Negative delay uses the WebAudio path. Some DRM players do not allow WebAudio to tap encrypted audio. On those, negative video delay may only work through canvas, and on some DRM live players neither path works.

Turn it on when audio arrives early instead of late - common with HDMI ARC/eARC soundbars, receivers with their own processing buffer, or Bluetooth transmitters that over-compensate. Video and audio delay values are stored separately.

Edge: if you see zero delay across every site after an update, disable/re-enable the extension and reload the tab. Firefox: some builds lack requestVideoFrameCallback and fall back to ~30 fps on canvas. Safari: OfflineAudioContext is not available on every build, limiting negative-delay.

Enable shortcuts in Settings -> Keyboard shortcuts. Click into the input field, then press the actual combo (for example Ctrl+Shift+ArrowUp). Some sites swallow keystrokes inside their player when it has focus.

None is sent anywhere. Stats (total sync time, session count, top sites, delay distribution) are stored locally on this device only. No telemetry, no account, no server. Turn it off in Settings -> Privacy.

Include browser + version, OS, site/content type, expected vs actual behavior, and whether reload reproduces it. Then run this in the affected tab console:

window.dispatchEvent(new CustomEvent('__btSyncCmd', { detail: JSON.stringify({ type: 'DIAGNOSE', msgId: 1 }) }));
window.addEventListener('__btSyncResp', e => console.log(JSON.parse(JSON.stringify(e.detail))), { once: true });

The mode field (canvas / mse / webaudio / none) tells us which pipeline picked you.