It’s possible that when you enable the Dynamic Background feature in the Turn Off the Lights options page, that your browser become slow. Because some of the Dynamic Background feature need more memory and use your hardware to render this visual effect. Especially the Cloud and Space background, those will use your hardware (GPU process).
Fix the slow extension
- 1 gigahertz (GHz) or faster processor
- 1 gigabyte (GB) RAM
- Video Cart 128 megabyte (MB) or higher
Also we recommend you to you the most secure web browser and that is Google Chrome where you have the latest improvement as browser engine to render and load a W3.org website.