v133 · performance

Freezing on Energy Saver

When Energy Saver is active, Chrome will freeze a "browsing context group" that has been hidden and silent for >5 minutes if any subgroup of same-origin frames within it exceeds a CPU usage threshold, unless it:

concepts

  1. Freeze on Energy Saver

    Chrome freezes background tabs more aggressively when the OS is in Energy Saver mode. Save state on the freeze event.

  2. Save-on-freeze

    A draft note that persists itself to localStorage in the freeze listener. Survives the 5-minute energy-saver freeze, tab switches, and tab close.

  3. Page lifecycle state machine

    A live visualisation of the active / passive / hidden / frozen / terminated transitions, with logged events and a ping timer that pauses on freeze.

  4. CPU threshold explainer

    Toggle your page's properties (audio, WebRTC, WakeLock, CPU level, hidden duration) and see whether Chrome would freeze it under Energy Saver. Includes a matrix of common tab types and a save-on-freeze code pattern.

why it shipped

When users activate "Energy Saver", they expect the browser to adapt its behavior to maximize battery life. Tab freezing on Energy Saver helps meet that expectation by preventing background tabs that aren't actively used from consuming CPU excessively.

references