Finding the differences between two blocks of text is a fundamental task. What alterations has another author or editor made to your document? How does one very long Excel formula differ from another at the character level? Note that Excel formulae need to be temporarily single quoted first before this Office add-in will fetch them (e.g. '=6*7 rather than =6*7) or directly copied into the add-in.
For years the desktop version of Word has had this functionality built-in. Excel is only just catching up, although finding differences at the character level between two cells of your choice isn’t built-in yet. Word Online has no built-in compare functionality at the time of writing.
Sometimes you just want to compare two regions of text that are in the same document or workbook. Or that you can quickly copy to your clipboard. Maybe you don't want to have to create new files, fire up an external application and navigate to the right directory.
You might just prefer using a novel diff algorithm.
Selection Diff Tool is intended to be at hand for when you just want to quickly compare two regions of plain text via selections or direct clipboard copying. It does not compare colors, styles, charts, tables or graphs.
One very useful feature is the optional ability to leave out unchanged paragraphs, lines or rows from the difference report. Navigation from one difference to another is good, but sometimes you just want to see all the differences at once.
For Excel, the add-in can fetch both single and multiple cell selections, so long as the latter are contiguous. Multiple cell selections obtained by clicking a row or column header such as A, B, C, 1, 2 3 do not work. However there is a workaround. Simply copy the whole row or column to the clipboard via ctrl-c and then paste it into one of the two text boxes via ctrl-v. Manually copying (ctrl-c) and pasting (ctrl-v) into the two text boxes always works.
Where supported, this add-in will appear on the Review tab.