Jitter Lens

Jitter Lens starts a measurement session only after you launch it on the active tab. It uses the browser's Layout Shift PerformanceObserver entries to count unexpected cumulative shifts, distinguish entries after recent input, highlight attributed elements, and display a short local event timeline. The panel can clear its current timeline or export up to 100 recent events as a JSON file when you request it. Closing the panel disconnects observation; navigating away also ends the session. Some shifts cannot be attributed to a specific element, and the numbers describe the current observation session rather than an audited page score. The extension does not monitor other tabs, upload measurements, or modify page content beyond its temporary overlay.