Check-as-you-type spell checking for Flex, Flash, and AIR Spelling Plus Library (SPL) is a full featured client-side spell checking engine, designed to be used in Flash, Flex and AIR; by both developers and designers. It was built as a best of breed library, with careful attention to architecture, optimization, and extensibility. February 27th, 2013: SPL is now open source. You can get the source