How to Merge Two Word Documents to Compare Changes

To compare two Word documents, open Word for Microsoft 365 on Windows and choose Review > Compare > Compare, select the earlier file as the original and the later file as the revised version, then choose OK. Word creates a separate comparison document that marks additions, deletions, and other differences, leaving the two source files unchanged. This is useful for reviewing edits without checking each document side by side.

What You’ll Need

Microsoft Word for Microsoft 365 desktop app on Windows. The Compare feature is also available in desktop versions of Word for Mac, though the ribbon layout can vary slightly. Word for the web does not provide the full desktop Compare command; open the documents in the desktop app.
Both documents saved as files that Word can open, preferably in a Word format such as .docx. Keep a copy of each source file so you can refer back to the exact versions you compared.
A clear idea of which file is the earlier or approved version and which one contains the proposed edits. Word uses these labels to organize the comparison, so choosing the right roles makes the result easier to interpret.

Step-by-Step

Save and identify both files. Save any open edits before comparing. Give the files names that distinguish their roles, such as Policy-original.docx and Policy-revised.docx. The names do not affect the comparison, but they make it less likely that you will select the wrong version. If either document is currently open, close it before proceeding if Word reports that the file is locked or unavailable.
Open the Compare command. Start Word and open a blank document or any document; the comparison does not replace the file currently open. Select the Review tab on the ribbon. In the Compare group, choose Compare, then choose Compare… from the menu. In some Word builds the command is labeled Compare Documents. Do not choose Combine if your goal is to inspect differences: Combine is intended to bring together edits from multiple reviewers.
Choose the original document. In the Compare Documents dialog, use the folder or browse button beside Original document. Locate and select the earlier version, then confirm the selection. This is the reference copy against which Word checks the other file. If the file is listed among recent documents, still verify its full name and location before continuing.
Choose the revised document. Use the browse button beside Revised document and select the later version containing the changes you want to review. Check that the original and revised fields do not point to the same file. The order matters for labels: text present only in the revised version is generally shown as an insertion, while text missing from it is shown as a deletion.
Set the comparison label and options. In Label changes with, enter a short label, such as Reviewer or Version 2. This label helps identify the comparison’s markup; it is not a claim about who actually made each edit. Choose More or More… to review available comparison settings. You can include or exclude categories such as formatting, comments, tables, headers and footers, or text boxes, and choose whether to compare changes at the word or character level. Keep the categories you need selected. If you only care about wording, excluding formatting differences can reduce visual noise.
Choose where Word displays the results. Find Show changes in and select New document for a separate result. This is usually the clearest and safest choice because it preserves both inputs and creates a third document containing the comparison. Other available choices can display markup in the original or revised document; use those only if you specifically want the results shown in one of the source files. Check the dialog once more: the earlier file should be Original, the later file Revised, and the output should be where you expect.
Run the comparison and inspect the markup. Select OK. Word processes the files and opens a comparison document with changes marked using Track Changes-style markup. Deletions and insertions may appear as balloons or inline marks, depending on your display settings. Use the Reviewing Pane from the Review tab if you want a list of changes, and use the Previous and Next controls in the Changes group to move through them. Read changes in context; a marked difference does not automatically mean the revised wording is better or correct.
Save the result as a new file. Choose File > Save As, select a folder, and give the comparison a distinct name, such as Policy-comparison.docx. Keep the original and revised files too. The result is a review document, not a permanently merged replacement for the two inputs. If you need a clean final document, decide which changes to keep in the comparison and use Accept or Reject in the Review tab, then save that approved version under another name.

On Mac: Open the documents in Word for Mac and look on the Review tab for Compare or Compare Documents. Select the original and revised files in the dialog, check the comparison options, and choose to show changes in a new document. Ribbon placement and labels can differ by Word release, so if you do not see the command, use Word’s search box to search for Compare. Word for the web may offer basic review tools, but use the desktop app for this document-to-document comparison workflow.

Common Mistakes

Reversing the two files. If the later copy is selected as Original, additions and deletions can appear backwards relative to your expectations. Confirm the roles in the dialog before you run the comparison. If the result reads in the wrong direction, rerun Compare with the files swapped rather than trying to interpret confusing markup.
Expecting Word to combine files into one clean document. Compare produces a marked-up third document that helps reveal differences; it does not automatically choose the preferred wording or create a polished final copy. Review the changes and accept or reject them deliberately.
Comparing unrelated versions. If one file has been substantially rewritten, moved, or reformatted, Word may show many changes even where the meaning is similar. Confirm that the two documents are genuinely versions of the same material before treating every mark as a small edit.
Ignoring formatting or comments settings. Excluding a category can hide changes you need to see, while including every category can make a simple wording review cluttered. Check the More options before starting and rerun the comparison if you discover that an important type of change was excluded.
Saving over a source file. Choosing an original or revised file as the display destination, or using the same name in Save As, can make the result difficult to distinguish from an input. Use New document and save the output with a new filename.

Tips

Use descriptive filenames and, when useful, include dates or version numbers. For example, Contract-v3-original.docx and Contract-v4-proposed.docx communicate both the relationship and the direction of the review.
Choose word-level comparison for ordinary prose because it is usually easier to read. Character-level markup can help when checking spelling, punctuation, or small changes inside a word, but it may create more individual marks.
Consider whether formatting, comments, headers, footers, and tables matter to your task. For a content-only review, hiding formatting changes can make the markup easier to scan. For a publication or template review, include formatting and structural elements.
Use the Reviewing Pane and Previous/Next controls to move systematically through a long result. For each change, check the surrounding paragraph, table, or heading rather than judging a word in isolation.
Keep the comparison document separate from the clean final copy. After the review, save the accepted version under a fresh name and retain the marked comparison as an audit trail if you may need to explain what changed.

Troubleshooting

The Compare command is missing or unavailable. Make sure you are using the desktop Word app rather than Word in a browser, and select the Review tab. If the ribbon is simplified or collapsed, expand it or search Word for Compare. On Mac, check the Review tab or search for Compare Documents because the command’s placement can vary with the release.

Word cannot open or select a file. Confirm that the document is saved locally or in a location you can access, and that it is not still being edited by another process. Close and reopen Word if a file remains locked. If a document is in an unsupported or damaged format, open it first and use File > Save As to save a fresh .docx copy, then compare those copies. Do not overwrite the only original while converting.

The result shows too many differences. First verify that you selected the right pair of versions. Then open Compare again and review the More options, especially whether formatting and other non-text categories are included. If the files have been reformatted or their content moved around, Word may mark extensive changes; inspect the result carefully and compare sections in context rather than assuming every mark represents a simple edit.

The result appears blank or misses changes. Confirm that the two selected files are not identical and that you did not choose the same file twice. Check whether relevant categories, such as comments or formatting, were excluded. Also confirm that you are viewing markup: on the Review tab, set the display to show the changes rather than hiding markup. If one source already contains unresolved tracked changes, make a copy and decide whether to accept or reject those existing revisions before comparing; otherwise, old markup can make the new result harder to understand.

Word freezes or takes a long time. Large documents with many images, tables, or tracked revisions can take longer to compare. Close unnecessary documents and applications, then try again with copies of the files. If the comparison still fails, save each source as a new .docx file and compare those versions. For a very large file, split the material into logical sections only if you can preserve headings and context; compare the full documents first when a complete review is important.

Frequently Asked Questions

Does comparing documents change either original file?
Not when you choose New document. Word creates a separate comparison result and leaves the selected source files as they were. Save the result with a new name, and avoid choosing a source as the place to display changes if you want to keep the inputs untouched.

Is Compare the same as Combine in Word?
No. Compare marks differences between two versions so you can review them. Combine is for bringing together revisions from multiple copies, often when different reviewers have edited a document. Choose Compare when you want a side-by-side version check represented as markup.

Can I compare two documents in Word for the web?
The full Compare Documents command is a desktop Word feature. If you are working in Word for the web and cannot find it, open the files in the desktop app, run Review > Compare > Compare, and save the comparison result. You can then store or share that result as appropriate.

Can Word compare documents with different filenames?
Yes. Filenames do not need to match. Word compares the document contents and selected categories, so different filenames are often helpful for distinguishing the original, revised, and comparison result.

Can I compare documents with comments or tracked changes?
Yes, but existing review markup can complicate the result. Decide whether existing tracked changes should remain part of the versions you compare. If you want to compare the underlying text cleanly, make copies and accept or reject earlier revisions in those copies before running Compare. Review comments separately if they are important to your decision.

How do I make a clean final document after comparing?
Review the comparison and use Accept or Reject in the Review tab for each change you want to decide. When the text is approved, save the resulting document under a new filename. Keep the comparison and source files if you need to refer back to the review history.

Try it: the Date Difference Calculator: days, months, years and weekdays between two dates, with the DATEDIF formulas.

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Sources: Function behaviour and menu paths: Microsoft Support documentation for Excel. Method & sources

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