Three ways to compare Word files

Someone sends back “the latest version” without tracked changes, or with tracked changes you don’t trust. You need to know exactly what is different from the copy you sent. There are three practical ways to find out.

1. Word’s built-in Compare

Desktop Word has a comparison command. Microsoft’s instructions are: open one of the two versions, go to Review › Compare › Compare Documents, choose the original in the first list and the revised file in the second, then select OK. Word opens a third document showing the differences as tracked changes, with the two originals alongside.

If you have desktop Word and both files are .docx, this works well and costs nothing extra. It is less handy when you don’t have desktop Word on the machine you’re using, when one of the versions is a PDF (a signed copy, say), or when you want a redline you can send as a PDF without fiddling with print settings.

2. Reading the two side by side

For a one-page letter, two windows next to each other will do. For anything longer it is how changes get missed: a “not” added to a sentence, a date moved by a week, a clause that quietly swapped places with another. Eyes skip over text they expect to see.

3. A comparison tool

RedlineKit, the tool on this page, reads both .docx files in your browser and compares them word by word. Nothing is uploaded: the files are opened by the page itself, which is why it works on a work laptop where you’re not allowed to send documents to unknown websites.

How to compare two Word documents with RedlineKit

Drop the earlier version on Original and the later one on Revised. Got them the wrong way round? Press the swap button between them.
Press Compare. A typical contract takes well under a second.
Read the summary: how many insertions, deletions, replacements and moves, and how many words were added and removed.
Step through the changes with the arrow buttons or the J and K keys, or click any change in the numbered list.
Switch between side by side (old on the left, new on the right, paragraphs lined up) and inline (one column, deletions struck through in red, insertions underlined in blue). Tick Changes only to fold away the paragraphs that didn’t change.

Compare two files now Free on screen. Files stay on your device.

What gets compared

The body text of each document, including text in tables and numbered lists. Paragraphs are lined up first, so an edited paragraph is compared with its own earlier version even when paragraphs were added or removed around it, and then the words inside are compared. A paragraph or a run of four or more words that was cut from one place and pasted somewhere else is shown as a move in green, not as an unrelated deletion and insertion.

Automatic list numbers (1., 1.1, (a)) are shown next to each paragraph, but renumbering alone isn’t counted as a change between two Word files, because inserting one clause would otherwise “change” every number after it.

Some things are not compared, and it’s worth knowing which:

Formatting. A word that only became bold is not marked.
Headers, footers, footnotes, comments and text boxes. Only the main body is read.
Existing tracked changes. A file that already has tracked changes is compared as if they had all been accepted.
Old .doc files. Save them as .docx in Word first.

Getting the result out

Viewing the comparison is free, as often as you like. If you need it as a file, one credit exports the pair as a PDF redline (numbered changes in the margin, ready to email) and as a Word document with tracked changes: the revised file, with each difference recorded as a tracked insertion or deletion your reader can accept or reject in Word’s Review tab. See turning two versions into tracked changes for how that file is built.

Tips for a clean comparison

Compare against the exact copy you sent, not an earlier draft of your own, so you only see the other side’s edits.
Smart quotes and straight quotes count as the same, and extra spaces are ignored, so retyped punctuation doesn’t drown the real changes.
Use Ignore case when one version has headings in capitals and the other doesn’t.

Compare two Word documents