Firefox Community Forum

Hello Firefox Support,

I am experiencing a consistent and disruptive performance issue that occurs immediately after certain complex web pages (particularly those with heavy scripting or dynamic content) have fully loaded.

The symptom is a temporary but complete freeze of the Firefox window, often lasting between 5 to 10 seconds, during which time the browser is completely unresponsive. This freeze is accompanied by a significant spike in CPU usage (often reaching 90-100%, according to Task Manager/Activity Monitor).

Details:

Trigger: The freeze reliably occurs right after the page status changes from "Loading" to "Done." I suspect it is related to post-load scripting execution or rendering finalization.

Impact: Any ongoing user interaction is halted until the spike subsides.

Tested Scenarios: I have replicated this on multiple sites, including heavy news aggregators, social media feeds, and complex web applications.

Troubleshooting: This issue persists even after:

Clearing cache and cookies.

Running Firefox in Safe Mode (disabling all extensions).

Creating a new, clean Firefox profile.

This severely degrades the browsing experience, especially when quickly navigating between tabs or starting a session.

Could you please investigate potential issues within the core rendering engine or script execution scheduler that might be causing these severe post-load processing bottlenecks?

Thank you.

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Using Firefox 146.0.1 (64-bit) on Mac (2.4 GHz 8-Core Intel Core i9, AMD Radeon Pro 5500M 4 GB, Intel UHD Graphics 630 1536 MB, 16 GB 2667 MHz DDR4, macOS 15.7.3)

I've used Firefox for years, but recently Firefox is unusable on Mac OS 15.7.2 because it's hogging all the RAM over time. I get a spinning beachball on my MacBook Pro. I look at the RAM being used and it's even over what I have in the computer. I have and always keep Firefox updated to the latest version.

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Firefox 146.0 (aarch64) MacBook Pro 16-inch, 2023 macOS 15.5 (24F74)

Any ideas?