Back in 2005, I wrote up my study of US and UK spelling differences and published a comprehensive* list. Over the next 8 years, it’s by far the article that I’ve had the most feedback on, most of it noting one or two spellings that I missed. I eventually stopped updating the page, but since I continue to get notes, I’ve decided to do a full update and present this as a central repository for the list in an easier-to-read format.