To open in Safe mode, either you can select it from the programs menu or type firefox -safe-mode in run command. You can also check Firefox memory usage by opening Firefox in safe mode by disabling all add-ons. Few things to take care while installing and using add-ons We are tempted to try out each and every fancy add-ons and these could slow down Firefox. One of the primary reasons of Firefox slowing down is due to large number of installed extensions.
