A Mac user will probably give you a better answer. Does a Mac have utilities to show you Memory and CPU use. It will depend not only on what number of tabs but also what the tabs are, video will be using memory and CPU, web-mail is probably surprisingly heavy on memory. *How many tabs do you usually have open at once and how many do you want to keep open ? <br/> (you could instead handle tabs in groups of bookmarks and keep less open) *How much RAM is on your system? <br>(You probably need to know whether your system is being forced to [http://en.wikipedia.org/wiki/Paging page] the memory and use the HDD for swap files, that causes the big slow down) See also * [[high memory usage]] * [[firefox consumes a lot of cpu resources ]] Note also Firefox shows where your memory is being used. The feature ''about:memory'' is relatively new and still being developed, key into the location bar '''about:memory'''