I maintain a small online text diff that people mostly use for contracts, price lists and CVs, not code. Its search traffic told me something I had not designed for: the queries were "compare two Word documents" , "compare 2 text files online" , "compare two PDF documents" . Nobody arrives holding two strings. They arrive holding two files. This post is the handful of decisions that turned a textbook LCS exercise into something that survives real documents. None of it is clever; all...