Chrome uses them for the "safe browsing" filter. Google HQ makes a bloom filter out of all the blocked websites and sends out the filter occasionally in an update. That way Chrome can test the URL you're about to visit for membership in the huge blacklist without taking much network/disk/memory/CPU. Of course there could be false positives but Chrome only has to phone home to double-check on possible matches. http://blog.alexyakunin.com/2010/03/nice-bloom-filter-applic...