Word's spell check is on by default, but you may need to turn it back on if you've disabled it

Microsoft Word checks your spelling as you type and marks errors with a red wavy underline. This happens automatically in most cases — you do not have to do anything to start the process. If you see red underlines under words, spell check is already running. If you do not see them, the feature has been turned off, and you can turn it back on in a few steps.

The steps differ slightly between Windows and Mac versions of Word, and between the desktop process and Word Online. This guide covers the most common setup: Word on Windows desktop.

Key Takeaways

  • Word checks spelling automatically as you type and marks errors with a red wavy underline beneath the word.
  • If you do not see red underlines, spell check is off and you can turn it back on through File > Options > Proofing.
  • You can right-click any red-underlined word to see suggested corrections or add it to your personal dictionary.
  • Word's spell check catches misspellings but not grammar errors or words used in the wrong context — those require the separate Grammar feature.

Turn spell check back on in Word for Windows

Open Word and go to the File menu in the top left. Click Options near the bottom of the menu. A window titled "Word Options" will open.

In the left sidebar, click Proofing. Look for the section labeled "When correcting spelling in Microsoft Office programs." You will see a checkbox next to "Check spelling as you type." If that box is empty, click it to turn spell check on. Then click OK at the bottom right to save the change.

Word will now mark misspelled words with a red wavy underline as you type. The change takes effect when ready in any document you have open.

Turn spell check on in Word for Mac

Open Word and click Word in the menu bar at the very top of the screen. Select Preferences from the dropdown menu. A new window will open.

Look for an icon that looks like a checkmark or the word Spelling and click it. You will see options for spell checking. Make sure the box next to "Check spelling as you type" is checked. Close the preferences window, and spell check will be active in your document.

Turn spell check on in Word Online

Word Online (the browser version you access through Office.com or your Microsoft account) has spell check turned on by default and does not have an on/off switch in the same way the desktop version does. If you do not see red underlines under misspelled words, the issue is usually that your browser is blocking the feature or you are using a browser Word Online does not fully support.

Try opening your document in a different browser, or switch to the desktop version of Word if you have it installed. If you are using an older browser version, updating it may restore spell check.

What to do when Word marks a word you know is correct

Word's dictionary does not contain every word — it may flag proper nouns, technical terms, or words from other languages. When you right-click a red-underlined word, a menu appears with options. Click Add to Dictionary to tell Word that word is correct and should not be flagged again.

If you want Word to stop flagging that word only in the current document, click Ignore All instead. The word will remain marked as an error in other documents, but Word will not underline it again in this one. Use "Add to Dictionary" for words you use regularly, and "Ignore All" for one-time exceptions.

The difference between spell check and grammar check

Spell check catches words that are spelled wrong. Grammar check (a separate feature, sometimes called "Editor" in newer Word versions) catches problems like subject-verb disagreement, missing punctuation, and words used in the wrong context. A word can be spelled correctly but used incorrectly — spell check will not catch that.

Grammar check is turned on separately and usually marks errors with a blue or green underline. If you want both features running, you may need to turn on grammar check as well through the same Proofing menu. The exact name and location depend on which version of Word you have.

Why spell check sometimes misses errors

Spell check only catches misspellings. It does not catch typos that happen to form real words — for example, typing "form" when you meant "from," or "their" when you meant "there." It also does not catch words that are spelled correctly but used in the wrong context, repeated words, or missing words.

This is why reading your work aloud or having someone else read it is still important. Spell check is a first pass, not a complete check. It catches obvious misspellings so you can focus on the things only a human reader will notice.

Frequently Asked Questions

Why is spell check not working even though I turned it on?

The most common reason is that you are using a language setting that does not match the words you are typing. If you are writing in Spanish but Word is set to English, it will mark Spanish words as errors. Check the language setting at the bottom right of the Word window (it usually says "English (United States)" or similar) and change it to match the language you are using.

Can I use a different dictionary or add my own words?

Yes. When you click "Add to Dictionary" on a red-underlined word, it goes into your personal dictionary, which Word uses from that point forward. You cannot easily swap in a completely different dictionary, but you can build your personal one word by word as you work. Some versions of Word also let you create a custom dictionary file, though this requires more technical steps.

Does spell check work in all parts of a Word document?

Spell check works in the main text of your document. It may not work in headers, footers, text boxes, or comments, depending on your Word version and settings. If you need those areas checked, you may have to enable them separately in the Proofing options.

What if I want spell check off for just one document?

You can turn spell check off globally (which affects all documents), but Word does not have a built-in way to disable it for a single document while keeping it on for others. Your best option is to use "Ignore All" for words you do not want flagged in that specific document, or temporarily turn off spell check in Options, work on that document, then turn it back on.