When you collaborate on a contract or a research paper, you might accidentally end up with two slightly different versions of the same file. Reading both documents side-by-side to manually find the missing sentences or altered paragraphs is exhausting and highly prone to human error. To instantly identify every single difference between two files, Google Docs includes a built-in “Compare Documents” feature that automatically generates a redline markup file.
How the Comparison Tool Works
The tool takes a base document and compares it against a secondary document. It then creates a brand-new, third document that highlights the differences as “Suggested Edits,” exactly as if someone had used the Track Changes feature.
- Open the first file (your base document) in Google Docs.
- Click on Tools in the top menu bar.
- Select Compare documents from the drop-down list.
- A small popup window will appear. Click the My Drive link to open the file picker.
- Search your Google Drive and select the second document you want to compare against, then click Open.
Attributing the Differences
Before you run the comparison, the popup window will ask you to fill out an “Attribute differences to” field. By default, this might show your own name.
It is highly recommended that you type the name of the secondary document here (e.g., “Version 2 Changes”). Because the final output file displays the differences as Suggested Edits, this attribution name ensures that you know exactly where the new text came from. If you leave it as your own name, it will simply look like you suggested the edits yourself.
Once you have set the attribution name, click the blue Compare button.
Reviewing the Redline Document
Depending on the length of the files, the comparison process may take a few seconds. Once it finishes, Google Docs will display a notification saying “Comparison is ready.” Click the Open button on that notification.
A completely new tab will open containing a document titled “Comparison of [Document A] and [Document B].”
As you scroll through this new document, any text that exists in Document A but is missing from Document B will have a strike-through line across it. Any text that was added to Document B will be highlighted in a bright color. You can use the standard Suggesting Mode tools on the right margin to Accept (checkmark) or Reject (X) each difference, allowing you to easily merge the two files into one perfect final draft.