Spell checker is on by default in Word, 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 squiggly underline. This happens automatically in most cases — you do not need to do anything to start the process. If you do not see red underlines under misspelled words, spell checker is either turned off or set to ignore certain types of errors. The steps to turn it back on depend on which version of Word you use and what you turned off.
The most common reason spell checker appears inactive is that you have disabled it in your settings, or you are working in a document that has a language set to "Do Not Check Spelling or Grammar". Both are straightforward to fix and take less than a minute.
Key Takeaways
- Word spell checker runs automatically by default and marks misspelled words with a red underline as you type.
- If you do not see red underlines, check your language settings first — the document may be set to "Do Not Check Spelling or Grammar".
- In Word for Windows, turn spell checker back on through File > Options > Proofing, then check "Check spelling as you type".
- In Word for Mac, go to Word > Preferences > Spelling and Grammar and select "Check spelling as you type".
- You can also right-click a word and select "Ignore All" or "Add to Dictionary" to control which words spell checker flags.
Turn on spell checker in Word for Windows
Open Word and go to File in the top left corner. Click Options at the bottom of the menu. A window titled "Word Options" will open.
In the left sidebar, click Proofing. Under the section labeled "Spelling", look for the checkbox next to "Check spelling as you type". If the box is empty, click it to turn spell checker on. If the box already has a checkmark, spell checker is already enabled and the problem lies elsewhere — skip to the language settings section below.
Click OK at the bottom right to save your changes. Spell checker should now mark misspelled words with a red underline as you type.
Turn on spell checker in Word for Mac
Open Word and click Word in the menu bar at the very top of your screen. Select Preferences from the dropdown menu.
In the Preferences window, find and click Spelling and Grammar. Look for the checkbox labeled "Check spelling as you type" and make sure it is checked. If it is not, click the box to enable it.
Close the Preferences window. Spell checker will now run in the background and mark errors with a red underline.
Check the language setting if spell checker is still not working
Even with spell checker turned on, Word will not mark errors if your document language is set to "Do Not Check Spelling or Grammar". This setting overrides the spell checker preference and is sometimes applied by accident.
Select all text in your document by pressing Ctrl + A (Windows) or Command + A (Mac). Go to Review in the ribbon menu at the top. Click the arrow next to Language and select Set Proofing Language. A dialog box will open. Make sure "Do Not Check Spelling or Grammar" is unchecked. Click OK.
If you only want to check spelling in part of your document, select just that text before following these steps. This is useful if you have quoted text in another language or technical terms you do not want flagged.
Understand what spell checker marks and what it ignores
Word spell checker compares words against its built-in dictionary. If a word is not in that dictionary, it gets marked with a red underline. This includes correctly spelled words that are straightforward uncommon — proper names, technical terms, brand names, and slang often get flagged even though they are spelled correctly.
You can tell Word to stop flagging a word by right-clicking it and selecting Add to Dictionary. The word will no longer be marked as an error in any document you create. You can also select Ignore All to stop flagging that word in only the current document.
Spell checker does not catch words that are spelled correctly but used in the wrong context — for example, "their" instead of "there". For that, you need grammar checking, which is a separate tool. Grammar checking is also turned on by default in most versions of Word and marks errors with a blue underline.
Turn off spell checker if you want to disable it
Some people turn off spell checker because the red underlines are distracting, or because they work with a lot of technical or specialized language that gets flagged constantly. If you want to disable spell checker, follow the same steps as turning it on — just uncheck the box next to "Check spelling as you type" instead of checking it.
You can also right-click any red underline and select Ignore All to stop flagging that specific word without turning off spell checker entirely. This is useful if you have a name or term that appears many times in one document.
Frequently Asked Questions
Why does spell checker mark words I know are spelled correctly?
Word's dictionary does not include all proper names, technical terms, brand names, or very new words. Right-click the word and select "Add to Dictionary" to stop it from being flagged in future documents. You can also select "Ignore All" to stop flagging it in only the current document.
Can I use a different dictionary or add my own words?
Yes. When you add a word to the dictionary, Word stores it in a custom dictionary file. You can also create multiple custom dictionaries for different types of work. Go to File > Options > Proofing > Custom Dictionaries to manage them.
What is the difference between spell checker and grammar checker?
Spell checker marks words that are not in the dictionary (red underline). Grammar checker marks sentence structure, punctuation, and word choice errors (blue underline). Both run by default in Word, but you can turn either one off separately in the Proofing settings.
Does spell checker work in Word Online?
Yes, but the settings are slightly different. In Word Online, spell checker is always on and you cannot turn it off. You can right-click flagged words to ignore them or add them to your dictionary, just like in the desktop version.