A computer-implemented process identifies useful alternative spellings of search strings submitted to a search engine. The process takes into consideration spelling changes made by users, as detected by programmatically analyzing search string submissions of a population of search engine users. In one embodiment, an assessment of whether a second search string represents a useful alternative spelling of a first search string takes into consideration (1) an edit distance between the first and second search strings, and (2) a likelihood that a user who submits the first search string will thereafter submit the second search string, as determined by monitoring and analyzing actions of users.