How word diff checker works
A line diff tells you which paragraphs changed; a word diff tells you which words inside them changed. This tool splits both texts into words, finds the longest sequence of words they share in order using the same longest-common-subsequence technique that version-control systems use, and then shows the words outside that shared sequence as inserted or deleted — inline, right in the flow of the text.
Two options make the comparison smarter. Ignore case treats "Hello" and "hello" as the same word, and ignore punctuation compares "now!" and "now?" as equal while still showing the original spelling in the output. A similarity score — the share of words the two texts have in common, relative to their combined length — summarizes how far apart the two versions are at a glance.
The result is presented as flowing text where inserted words are marked as insertions and removed words as deletions, so a sentence rewrite reads naturally from left to right. The Copy button produces wdiff-style plain text, with deleted words wrapped in [- -] and added words in {+ +}, the same convention the classic wdiff command-line utility uses.