High CPU usage after resume from sleep with many open tabs

dinamikler — Thu, 30 Apr 2026 03:30:02 GMT

Product: Mozilla Firefox
Version: 150.0.1 (64 bit)
OS: (Windows Version 10.0.19045.6466)

Description:
When the system resumes from sleep/hibernate with a large number of open tabs (hundreds), Firefox causes CPU usage to spike to 100% for an extended period. During this time, the entire system becomes very slow and unresponsive until CPU usage returns to normal.

Steps to reproduce:

Open a large number of tabs (100+ or more)
Put the computer into sleep/hibernate
Resume the system
Observe CPU usage and system responsiveness

Expected behavior:
Firefox should restore tabs gradually or in a resource-efficient way without maxing out CPU or freezing the system.

Actual behavior:
CPU usage spikes to 100% for several minutes, making the system sluggish.

Additional notes:

This issue seems more noticeable with session restore enabled
Possibly related to tab restoration or background processes after resume

Suggestion:
Consider implementing a more gradual/lazy tab restoration or limiting CPU usage during session recovery.

Thanks.

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High CPU usage after resume from sleep with many open tabs