We made yet another change to how we run the memory tests. First, we're using the about:memory flag to calculate total memory usage for Chrome. Since Chrome runs each tab in a separate process, there is a slight amount of memory shared between processes. Windows Task Manager can double-count this shared memory. Although such double-counting only ends up amounting to 50 MB or so in a 1+ GB 40-tab load, the about:memory flag is more accurate.
The memory totals of the other Web browsers are still tallied using Windows Task Manager.
Internet Explorer remains the lightest Web browser when it comes to the memory footprint of loading a single tab. Chrome 14 drops Google from second down to fifth, though it's still under 75 MB. Meanwhile, Firefox 7 moves Mozilla up from fourth place to second. Safari remains smack in the middle, while Opera moves up to fourth place.
When the load is changed to a hefty 40 tabs, Firefox 7 doesn't disappoint, shaving about 300 megabytes off the Firefox 6 tally from WBGP6. Safari drops to second place, though it's still comparatively sleek at under three-quarters of a gigabyte. Opera retains third place at over 800 megabytes, and Chrome 14 moves up to fourth place, utilizing just over one gigabyte. Internet Explorer drops to fifth, using the most amount of memory (an astounding 1.3+ GB).
Being the only browser to use less than a half gigabyte under heavy load and the second-place finisher at a light load (less than 50 MB), Firefox 7 is the clear winner. Safari takes second and Opera places third. IE9 and Chrome give us the poorest showings in raw memory usage. IE9's only saving grace is its super-low single-tab total.
We combined the two memory management tests into a single chart. The memory totals were recorded instantly after closing 39 of the 40 tabs, and once more five minutes later.
Chrome is the quickest to immediately release memory back to the operating system, followed by Internet Explorer. Opera comes in an even more distant third, trailed by Safari in fourth.
Surprisingly, the champion of memory usage (Firefox 7) does not give much of its monopolized memory back to Windows right away. After an additional five minutes, Chrome settles in at just 20 MB over its single-tab usage, while IE9 drops back down to just 10 MB over the single-tab tally. Firefox 7 finally gives all but 160 MB back to Windows after a few minutes. While this is still four times the memory tied up in a single tab, it is a good 100 MB less than Firefox 6. After the additional five minutes passes, Safari and Opera both drop down to around 350 MB, placing fourth and fifth (respectively).
Chrome is still a powerhouse when it comes to memory management, needing no time at all to release unused resources back to the operating system. IE9 needs a little more time, but remains incredibly efficient. Firefox 7 gives us the biggest surprise here, using the least amount of memory under a heavy load and dropping to just over 150 MB after five minutes. Safari and Opera are fairly mediocre in this discipline, though neither is as bad as they once were. Comparatively, they're at the bottom of the heap.
Naming a winner for overall memory efficiency is really tough this time, but we have to give the victory to Mozilla. Firefox 7 is simply never weak in our testing.