Word Compare Documents with Copilot AI in 2026: The Complete Review Guide

Document review is one of the most time-consuming tasks in any office. Contracts, proposals, policies, and reports go through multiple versions, and identifying exactly what changed between version 3 and version 7 of a 50-page document is a genuine productivity drain. In 2026, Microsoft Word combines its built-in Compare Documents feature with Copilot AI to make this process faster, smarter, and far less error-prone.

This guide covers the full workflow: from running a traditional comparison to using Copilot to summarise the changes and flag anything that needs your attention.

The Traditional Compare Documents Feature

Word has included a Compare feature for many years. It works by analysing two versions of a document and creating a third combined document that shows all differences as tracked changes, so you can see deletions in red strikethrough and insertions in blue underline.

How to Run a Document Comparison

Open Microsoft Word (the document you are currently editing does not need to be either of the compared files).

Click the Review tab in the ribbon.

Click Compare in the Compare group, then select Compare from the dropdown (not Combine).

In the Compare Documents dialog, choose the Original document (the older version) using the folder icon.

Choose the Revised document (the newer version).

Under Comparison settings, select which elements to compare: comments, formatting, tables, headers and footers, etc.

Under Show changes in, choose New document to keep both originals untouched.

Click OK. Word generates a comparison document with all differences marked as tracked changes.

Understanding the Comparison Result

The comparison result opens with three panels visible: the Revised Document on the left, the comparison markup in the centre, and the Original Document on the right. The Reviewing Pane lists every change with the line number and type of edit.

Use Accept All or Reject All in the Review tab to finalise changes, or step through them one by one with Accept/Reject buttons to decide on each edit individually.

Compare vs Combine: Knowing Which to Use

Compare: produces a single marked-up document showing what changed between two specific versions. Best for reviewing a document that went through revision by one person.

Combine: merges tracked changes from multiple reviewers into one document. Best when several people have edited separate copies and you need to bring all their edits together.

Rule of thumb: if you have two versions and want to know what changed, use Compare. If you have three people's edits to merge, use Combine.

Using Copilot to Review Document Changes

In 2026, the most powerful addition to the document review workflow is Copilot integration. After generating the comparison document, open the Copilot pane (click the Copilot button on the Home tab) and ask it to analyse the changes for you.

Summarise All Changes

Type a prompt such as: "Summarise all the changes in this document and group them by type." Copilot reads the tracked changes and returns a structured summary like:

Clause modifications: Section 4.2 liability cap changed from $50,000 to $100,000. Section 7.1 payment terms changed from Net 30 to Net 14.

New content added: A new confidentiality section (Section 12) was added covering data handling obligations.

Deleted content: The previous Section 9 on dispute resolution was removed entirely.

Formatting changes: 14 instances of heading style changes and 3 table restructures.

Identify High-Risk Changes

For contract and legal document review, try: "Which changes in this document could have legal or financial implications?" Copilot flags modifications to payment terms, liability clauses, termination conditions, and obligation language, helping you prioritise what to review carefully versus what is low-risk boilerplate cleanup.

Ask About Specific Sections

You can ask Copilot targeted questions: "What changed in Section 5?" or "Did anything change regarding the indemnification clause?" Copilot searches the tracked changes and provides a direct answer, saving you from manually scanning through hundreds of changes to find the one that matters.

Version History: An Alternative to Manual Comparison

If both document versions were saved in OneDrive or SharePoint, you may not need to run a manual comparison at all. Word's Version History (File > Info > Version History) shows every saved version of the document with timestamps and author names.

In 2026, Copilot can compare any two versions directly from Version History. Open version history, right-click any two versions, and select Compare with Copilot. This triggers the same AI-assisted comparison workflow without you needing to locate and download the old files separately.

Tips for a More Efficient Document Review

Always compare in a New document so you never accidentally overwrite either original.

Use the Filter by author dropdown in the Reviewing Pane to focus on changes made by specific reviewers when multiple people edited the document.

Click Show Markup > Specific People to show or hide tracked changes from individual authors.

Use Copilot to generate a change log summary you can paste into the email to stakeholders, saving time on the review communication.

For very long documents, ask Copilot to "list only the substantive content changes, ignoring formatting edits" to cut through the noise.

Enable the document to always save to OneDrive AutoSave so Version History is always available for comparison.

Comparing Documents in Word for the Web

Word for the web (office.com) includes a Compare feature under the Review tab, but with fewer customisation options than the desktop app. In 2026, the web version has improved significantly and handles most standard comparison tasks. For complex legal or contract comparisons with extensive formatting analysis, the desktop app remains the more reliable choice.

Conclusion

Document comparison has always been an underappreciated feature of Microsoft Word. With Copilot AI added to the workflow in 2026, it has become genuinely powerful: not just showing you what changed, but helping you understand which changes matter and why.

The next time you receive a revised contract or policy document, run the Compare tool and then open Copilot to ask it to flag anything significant. What used to take an hour of careful reading now takes ten minutes of focused review on the changes that actually matter.

Try this workflow on any two versions of a document today. You will be surprised how quickly Copilot can surface the one clause buried on page 34 that changed everything.