Mozilla Tests Firefox "Tab Warming"

According to a description of the feature, Tab Warming will watch the user's mouse cursor and start "painting" content inside a tab whenever the user hovers his mouse over one.

Firefox will do this on the assumption the user wants to click and switch to view that tab and will want to keep a pre-rendered tab on hand if this occurs.

"For many cases, I don’t actually think tab warming will be very noticeable," Conley said. "In my experience, we’re able to render and upload the layers for most sites quickly enough for the difference to be negligible."

As the expert said, the gain is measured in milliseconds, but in some cases this will prevent users from viewing a blank or incompletely rendered page when switching tabs.