What an index is and why you might want one

An index in Word is a list of terms and page numbers that appears at the end of a document. When you mark certain words or phrases throughout your document as "index entries," Word collects them, alphabetizes them, and shows you exactly which pages they appear on. This is useful for longer documents — manuals, research papers, books — where a reader needs to find specific topics quickly without scrolling through everything.

The index itself is not something you type manually. Instead, you tell Word which words matter, and Word builds the list for you automatically. If you later add or delete pages, you can update the index and the page numbers adjust on their own.

Key Takeaways

  • Mark index entries by selecting a word, going to the References tab, and clicking "Mark Entry" — you can mark one word at a time or mark all instances of a word at once.
  • Word stores your marked entries invisibly in the document; you can see them only if you turn on formatting marks or look in the Index dialog.
  • Once you have marked all the terms you want, place your cursor where you want the index to appear (usually the end of the document) and insert it from the References tab.
  • After you add or remove pages, right-click the index and select "Update Field" to refresh the page numbers.
  • You can choose from several index styles — a straightforward two-column layout, a run-in format, or a more detailed version with subentries — depending on how your document looks.

How to mark words as index entries

Start by opening your document and finding the first word or phrase you want to include in the index. Select that word by clicking and dragging across it, or double-click a single word to select it. The selection must be exact — if you select extra spaces or punctuation, the index entry will include them too.

Once the word is selected, go to the References tab at the top of the ribbon. Click the Mark Entry button (it looks like a bookmark with a mark). A dialog box opens. The selected text appears in the "Main entry" field. You can leave it as is, or you can type a different version if you want the index to show something slightly different from what appears in the document. For example, if your document says "COVID-19" but you want the index to list it under "Coronavirus disease 2019," you would type that in the Main entry field.

Click Mark to mark just this one instance, or click Mark All to mark every instance of that word throughout the entire document. Mark All is faster if you have a term that appears many times and you want all of them in the index. After marking, close the dialog by clicking the X button.

Marking subentries and creating a hierarchy

If you want your index to show related terms grouped under a main heading, you can create subentries. For example, you might have "Vegetables" as a main entry, with "carrots," "spinach," and "tomatoes" as subentries underneath it.

To do this, select the word you want as a subentry. Open the Mark Entry dialog again. In the "Subentry" field, type the main heading you want it grouped under. So if you are marking "carrots" and you want it under "Vegetables," type "Vegetables" in the Subentry field and "carrots" in the Main entry field. Click Mark. When the index builds, it will show "Vegetables" with "carrots" indented below it.

You can also create a second level of subentries — a subentry under a subentry — by using the colon format. In the Main entry field, type "Vegetables:Root" to create a hierarchy where "Root" appears under "Vegetables." This works for one level of nesting; Word does not support deeper hierarchies in the standard index.

Inserting the index into your document

Once you have marked all the terms you want to include, place your cursor at the location where you want the index to appear. Most documents put the index at the very end, after all the body text. You can insert it on its own page if you want — just press Ctrl+Enter to create a page break before inserting the index.

Go to the References tab and click Index. A gallery of index styles appears. Choose the style that matches your document's look. The "Automatic Table" styles show a straightforward two-column layout; the "Modern" and "Formal" styles offer different visual treatments. Click the style you want, and Word inserts the index at your cursor position.

Word builds the index from your marked entries, alphabetizes them, and lists the page numbers where each entry appears. If a term appears on multiple pages, all page numbers show in the index.

Updating the index when your document changes

After you insert the index, you may add or delete content, which shifts page numbers around. The index does not update automatically. To refresh it, right-click anywhere in the index and select Update Field. A dialog appears asking whether you want to update page numbers only or the entire index. Choose Update entire table if you have added new marked entries since the last update, or Update page numbers only if you have only moved content around without adding new index entries.

You can also update the index by clicking anywhere in it and pressing F9. This is faster if you are updating frequently while editing.

Editing or removing index entries

If you want to change or remove an index entry after marking it, you need to find the mark itself. Turn on formatting marks by pressing Ctrl+* (or Ctrl+Shift+8 on some keyboards). Index marks appear as gray XE codes in curly braces, like { XE "carrots" }. You can click directly on the code and edit the text inside the braces, or delete the entire code to remove that entry from the index.

If you marked a term with Mark All and now want to remove it from the index entirely, you have two options: delete each individual mark by hand, or use Find and Replace to find all instances of the mark at once. To use Find and Replace, press Ctrl+H, check the "Find all" option, and search for the XE code. This is faster for terms that appear dozens of times.

After you edit or delete marks, update the index again by right-clicking it and selecting Update Field.

Choosing between a standard index and a concordance

The method described above — marking entries one by one — works well for documents where you control which terms matter. But if you have a long document and want to index many terms, Word offers an alternative called a concordance index. This method uses a separate table you create in another document that lists all the terms you want indexed. Word then finds those terms in your main document and builds the index automatically.

To create a concordance index, open a new blank document and create a two-column table. In the left column, type each term exactly as it appears in your main document. In the right column, type how you want it to appear in the index (or leave it blank if it should appear the same way). Save this table document. Then, in your main document, go to References > Index, click the "Options" button, and select "Concordance file." Choose your table document, and Word builds the index from it.

A concordance index is faster if you have 50 or more terms to index, but it requires more setup. For most documents, marking entries manually is simpler and gives you more control over what gets included.

Frequently Asked Questions

Can I create an index in Word Online, or do I need the desktop version?

Word Online does not support creating or inserting indexes. You need the desktop version of Microsoft Word (Windows or Mac) to mark entries and build an index. If you only have access to Word Online, you can type an index manually, but it will not update automatically when pages change.

What if a term appears on 20 pages — does the index show all 20 page numbers?

Yes, the index shows every page number where the term appears, separated by commas. If you want to limit this — for example, to show only the main discussion of a topic — you can mark some instances with a different main entry or straightforward not mark every occurrence. Mark only the pages where the term is most important.

Can I make the index entries clickable links?

Word does not automatically create clickable links in a standard index. However, you can manually convert the page numbers to hyperlinks by selecting each number, right-clicking, and choosing "Link." This is time-consuming for large indexes. Some users create a table of contents instead, which Word can make clickable automatically.

How do I delete an index and start over?

Click anywhere in the index and select the entire index (Ctrl+A while the cursor is in the index). Press Delete. The index disappears, but your marked entries remain in the document. You can then mark new entries or rebuild the index with different settings.

What happens to the index if I convert my Word document to PDF?

The index converts to static text in the PDF — it is no longer a field that updates. The page numbers in the PDF index should match the page numbers in the final Word document, but if you later edit the Word file and change page numbers, the PDF index will not reflect those changes. You would need to export to PDF again.