It happens to everyone. You’re deep into a three-page report or a late-night email, typing at a hundred words per minute, and you realize something is wrong. Usually, Microsoft Word is a sea of jagged red underlines, shouting at you for every "teh" and "recieve" you throw at the page. But right now? Nothing. Silence. The page is pristine, which would be great if you were a perfect typist, but you know for a fact you just mangled the word "maintenance."
If you need to know how to turn on spell checker in Word, you’ve likely bumped into one of the many toggles that Microsoft hides in its sprawling "Options" menu. It’s annoying. Honestly, it’s one of those things that should just work, but sometimes a random software update or a stray keyboard shortcut can knock the whole system offline. Microsoft Word's proofing engine is actually a pretty complex beast, pulling from local dictionaries and cloud-based AI, so when it breaks, there isn't always one single button to blame.
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The Quick Fix for a Broken Spell Checker
Most people just want the red lines back. Now.
First, check the Status Bar at the very bottom of your Word window. See that little book icon? If it has a tiny red "x" on it, Word has found errors but might not be showing them. If you click that book, it sometimes forces the Proofing pane to pop open on the right side of your screen.
But if that doesn't do it, you have to go into the belly of the beast. Click File, then look all the way down at the bottom left for Options. Once that window pops up—and it’s a big one—click on Proofing. This is the nerve center. You’re looking for a section called "When correcting spelling and grammar in Word."
Make sure the box labeled Check spelling as you type is checked. If it’s unchecked, Word is basically ignoring your typos until you manually run a scan. While you're there, look at the very bottom of that same menu. There’s a section for "Exceptions." If the box that says Hide spelling errors in this document only is checked, uncheck it immediately. This is a common culprit when spell check works in one file but not another.
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Why Your Language Settings Might Be Ruining Everything
Sometimes the "Check spelling as you type" box is checked, but Word still acts like it’s blind. This usually isn't a glitch in the software itself; it's a language tagging issue.
Word treats every paragraph—and sometimes every word—as having a specific language identity. If you accidentally highlight your text and the language gets set to something like "Uzbek" or "Sanskrit," and you don't have those proofing tools installed, Word simply gives up. It won't show red lines because it doesn't know what the "correct" version of the word should be.
To fix this, hit Ctrl + A to select your entire document. Go to the Review tab on the top ribbon. Click on Language, and then Set Proofing Language.
Here is the kicker: look at the bottom of that small pop-up window. There is a checkbox that says Do not check spelling or grammar. If that box has a checkmark or even a solid square in it, click it until it's completely empty. Then, make sure "English (United States)" or your preferred dialect is selected at the top. Hit OK. Suddenly, the red underlines usually flood back in like a dam breaking.
The Difference Between Word Online and Desktop
It's worth noting that how to turn on spell checker in Word looks a bit different if you're using the web version. Word Online (part of Microsoft 365) is a bit more streamlined—which is a polite way of saying it has fewer buttons.
In the browser version, you’ll find the Editor settings under the Home tab or the Review tab. Microsoft has been rebranding "Spell Check" as "Microsoft Editor." It’s a bit more advanced, offering "refinements" for things like conciseness or formality. If you’re not seeing any suggestions in your browser, check your browser’s own built-in spell checker settings (like in Chrome or Edge), as they can sometimes conflict with Word's native Editor.
When the Dictionary File Is Actually Corrupt
Every once in a while, the problem is deeper than a checkbox. Word uses a file called Custom.dic to remember the words you "Add to Dictionary." If this file gets corrupted or moved, the whole proofing engine can stutter.
Back in that File > Options > Proofing menu, click on the Custom Dictionaries button. You should see CUSTOM.DIC (default) in the list. if it's missing, or if there's an error message next to it, that's your smoking gun. You can usually fix this by creating a new one or re-linking the old one.
It's also possible that an Add-in is causing the drama. If you use Grammarly or ProWritingAid, those third-party tools sometimes "take over" the proofing duties and disable Word's native red underlines to prevent the screen from looking too cluttered. If you want the original Word spell check back, you might have to toggle those apps off temporarily.
Modern Features: The Editor Pane
Microsoft really wants you to stop thinking about "Spell Check" and start thinking about "Editor." If you press F7 on your keyboard, the Editor pane slides out. This is the modern way to handle errors.
Instead of right-clicking every single word, the Editor gives you a "Score" for your document. It categorizes issues into Spelling, Grammar, and Clarity. If you're working on a long-form piece of writing, this is actually a lot more efficient than hunting for red squiggles. It’s also where you’ll find the "Similarity" checker—which is basically a plagiarism tool—though that usually requires a paid Microsoft 365 subscription.
The AI-driven suggestions in the newer versions of Word are surprisingly good. They can catch "formally" vs "formerly," which a basic spell checker would miss because both are technically words. However, if you find the "Clarity" and "Conciseness" suggestions annoying (the blue and gold underlines), you can turn those off specifically in the Proofing options while leaving the red spelling lines active.
Moving Forward With a Clean Document
Once you've managed to get the engine running again, it’s a good idea to make sure it stays that way for all future documents.
- Open a blank document.
- Go to Review > Language > Set Proofing Language.
- Ensure the "Do not check spelling" box is unchecked.
- Click the Set As Default button at the bottom of the window.
- Confirm the change.
By doing this, you're updating the Normal.dotm template. This is the "DNA" of every new Word file you create. If the template is fixed, you won't have to keep digging through menus every time you start a new project.
If you are still seeing no red lines after all of this, the final "nuclear option" is to repair the Office installation. You do this through the Windows Control Panel (or Settings > Apps), finding Microsoft 365, and selecting "Modify" then "Online Repair." It takes a while, but it replaces any broken system files that might be preventing the proofing tools from loading.
The spell checker isn't just a safety net; it's a way to maintain professional credibility. A single "their" instead of "there" can undermine an entire proposal. Making sure these settings are locked in will save you the embarrassment of a late-night typo slipping through to your boss or a client.
To ensure your document is truly error-free, run a final manual check by pressing F7. This forces the software to re-scan the entire file from the first character to the last, catching any lingering issues that the "as you type" feature might have skipped over during a heavy editing session. If the Editor pane says "You've finished reviewing the Editor's suggestions," you're good to go.
Check your "Proofing" options one last time to ensure "Frequently confused words" is enabled; this is the specific setting that catches typos which are technically real words but used in the wrong context. Keeping this active ensures a much higher level of polish than basic spelling alone. If you find the auto-correcting behavior too aggressive—like when it changes names or technical jargon—simply add those specific terms to your Custom Dictionary as you go. Over time, Word will learn your specific vocabulary and stop flagging your unique terms as errors.