Compare two texts line by line, word by word or character by character, and copy a unified diff patch. Free online diff checker.
Compare two texts and highlight what was added and removed, by line, word or character. Copy the result as a unified diff patch.
Lines for code and config files, words for prose, characters for short strings.
The patch format used by git diff, with - for removed and + for added lines.
No fixed limit, but very large texts compared character by character can be slow.