How to Add an Index to a Word Document

An index in Word helps readers quickly locate specific terms, topics, and names in a long document. Instead of scrolling through dozens of pages, a reader can look up a keyword and find the exact page number where it appears. Word builds the index automatically after you mark each entry you want to include. This article explains how to mark index entries, generate the index, and update it when your document changes.

What the Index Feature Does and What You Need Before You Start

The index feature in Word scans your document for specially marked text and compiles a list of those terms with their page numbers. You control exactly which words appear in the index. Word does not guess or auto-detect terms. You must mark each entry manually or use a concordance file for batch marking.

Before you begin, ensure your document has finalized page breaks and section breaks. Adding or removing content after generating the index will shift page numbers. You will need to update the index to match the new page layout. No external tools or add-ins are required. The feature is built into Word for Windows and Word for Mac.

Understanding Main Entries and Subentries

A main entry is the primary term a reader looks up, such as “Formatting.” A subentry is a narrower term grouped under the main entry, such as “Paragraph” under “Formatting.” Word indents subentries below the main entry in the generated index. You can also create a cross-reference entry that points to another term, for example “See Formatting.”

Prerequisite: Finalize Your Document Structure

Finish writing and editing the document before marking index entries. If you later move large blocks of text, the page numbers in your index will become incorrect. Use Word’s heading styles (Heading 1, Heading 2, etc.) to organize content. The index does not depend on headings, but a well-structured document makes marking entries more predictable.

Steps to Mark Index Entries and Generate the Index

1. Select the term you want to index
   Highlight the word or phrase in the document. For example, select “watermark” if you want readers to find every page that mentions watermarks.
2. Open the Mark Index Entry dialog
   Go to the References tab and click Mark Entry in the Index group. Alternatively, press Alt+Shift+X. The dialog opens with the selected text already filled in the Main entry field.
3. Configure the entry options
   In the dialog, you can edit the Main entry text. To add a subentry, type it in the Subentry field. To create a cross-reference, select Cross-reference and type the target term. Leave the Current page option selected to show the page number. Click Mark to mark only this occurrence. Click Mark All to mark every occurrence of that exact text in the document.
4. Close the dialog and continue marking
   After marking, the dialog stays open so you can select the next term in the document and repeat the process. Word inserts a hidden XE (Index Entry) field code next to each marked term. These fields do not print and do not appear in the final document unless you show formatting marks.
5. Place the cursor where you want the index
   Move to the end of the document or to a dedicated index page. Insert a page break if needed. Go to the References tab and click Insert Index in the Index group.
6. Choose index formatting options
   In the Index dialog, select the number of columns (usually 2), the tab leader style, and the format (From template, Classic, Fancy, Modern, etc.). Check the Right align page numbers box if you want page numbers aligned to the right margin. Click OK. Word generates the index table at the cursor position.

Using a Concordance File for Batch Marking

If your document contains many repeated terms, create a separate Word document that lists each term in a two-column table. The first column contains the word to mark. The second column contains the index entry text. Save the file. Then in your main document, go to References > Insert Index > AutoMark. Select the concordance file. Word marks every occurrence of every term in the table automatically. This method saves time for large documents.

Common Mistakes and Limitations When Working With Indexes

Page numbers in the index do not match the actual pages

This happens when you add or remove content after generating the index. To fix it, right-click anywhere inside the index table and select Update Field. Or click the index and press F9. Word recalculates all page numbers based on the current document layout.

Mark All creates duplicate entries for slight variations

If the same term appears with different capitalization or punctuation, Mark All treats each variation as a separate entry. For example, “Word” and “word” produce two index entries. To avoid this, select all occurrences manually or use a concordance file with the exact text as it appears.

Index entries disappear after saving and reopening

Hidden XE fields remain in the document even if you do not see them. If the index table is missing, you may have accidentally deleted it. Reinsert the index by following Steps 5 and 6 above. The XE fields are still present, so the index will regenerate correctly.

Subentries are not indented in the generated index

This occurs when you type the subentry in the Main entry field instead of the Subentry field. Open the Mark Index Entry dialog for that occurrence and move the text to the correct field. Then update the index with F9.

Item	Mark Entry (Manual)	AutoMark (Concordance File)
Setup time	Slow for many entries; fast for a few	Fast for many entries after file is created
Control over subentries	Full control per occurrence	Limited to what is in the concordance table
Risk of duplicates	Low if you mark manually	Higher if terms have multiple forms
Best for	Short documents with 10-50 index terms	Long documents with hundreds of repeated terms

After you generate the index, press Ctrl+A then F9 to update all fields in the document, including the index. This ensures page numbers are accurate before printing or sharing. For a professional look, apply the built-in Index 1 and Index 2 paragraph styles to adjust font size, indentation, and spacing of the index entries.