Live Sync by Ulpio

Learning the result from chat before you see it on screen is annoying. Live Sync fixes that without you dragging the progress bar every few minutes.

HOW IT WORKS

The extension continuously measures the gap between what you are watching and the live edge. When that gap exceeds your target, it raises playback speed slightly until it catches up, then drops back to 1.00x on its own.

Two ways to catch up:

Smooth: speed scales with the size of the delay, almost always between 1.03x and 1.15x. You will not notice it.
Burst: applies a fixed speed (1.25x by default) until the gap is gone.

When the delay is too large to be worth recovering by speeding up, the extension jumps straight to the live edge instead.

MODES

Gentle — 6 s target, 1.07x cap. For shaky connections.
Balanced — 2.5 s target, 1.15x cap. The default.
Minimum latency — 1 s target, 1.30x cap.
Auto — tracks stalls and buffer health and adapts on its own: a struggling connection loosens the target, a stable one tightens toward the live edge.
Manual — you set target latency, maximum speed, burst speed and the jump threshold.

WHAT IT DOES NOT DO

Much of the work is knowing when to stay out of the way:

It stands down during ads.
It will not speed up on a short buffer, since doing that only causes stalls.
If you deliberately seek backwards to rewatch something, syncing pauses until you return near the live edge.
If you pick a different speed in the YouTube menu, that becomes the baseline and the correction applies on top of it instead of overriding your choice.

EXTRAS

Optional on-player readout with latency, speed and buffer.
The same live numbers in the popup.
Shortcuts: Alt+Shift+L jumps to live, Alt+Shift+K toggles the extension.
Works in embedded YouTube players too.

PRIVACY

No data leaves your browser. No telemetry, no servers, no remote code. Settings stay on your machine. The requested permissions are storage, activeTab and access to youtube.com and youtube-nocookie.com, which is where the extension needs to run.

LIMITATIONS

Streams on normal latency (not "low" or "ultra-low") have a delay floor set by YouTube itself. On those, very short targets may be unreachable and Gentle or Auto behaves better. Speeding audio up also shifts its timbre a little; pitch correction is on, but at 1.30x it is still noticeable.