Wikipedia
Diff-Text is a free software tool which finds the differences between two blocks of plain text. It takes the form of a collection of web-pages, each one with a slightly different layout. Text to be compared is pasted directly into the web-page. It can be used from any operating system.
Diff-Text was developed by DiffEngineX LLC and uses improved algorithms originally developed for the spreadsheet compare tool DiffEngineX
It allows the user to choose between comparing at the level of whole lines (or paragraphs), words or characters. If comparing whole lines only the fact that a line is not in the other block will be reported. Diff Text considers a paragraph to be any line ending with a Windows, Macintosh or Unix line terminator.
The website can combine the original and modified text blocks into one pane with all differences highlighted. Alternatively the marked-up original and modified text blocks can be displayed in individual panes.
Navigation from one difference to the next is supported.
All of the above features are not unique and can be found in other text comparison tools.
The software can display just the differences, the differences with a variable amount of context on either side or the whole marked-up text.
The website supports the use of https/SSL (Secure Sockets Layer) so confidential text can be compared.
The algorithm used by Diff Text is used by Selection Diff Tool, which is an app for Microsoft Word and Excel 2013.