Word spelling checker not installed error on Windows 10/11

You open an existing document or start typing in Word, run a spell check with F7, and get this: "Microsoft Word cannot start the spelling and grammar checker: The spelling and grammar check is not installed." Maybe you're on a corporate laptop that got pushed an Office update last night. Maybe you just installed a new language pack and now it's broken. The error shows up on Windows 10 and Windows 11 across Office 2016, 2019, 2021, and Microsoft 365.

What's actually happening here?

Word's spell checker lives inside a set of DLLs and data files called the proofing tools—dictionaries for various languages, a grammar engine, and a thesaurus. Each language has its own set. When you install Office, it installs proofing for whichever language your Office matches. If you later add a language pack, or if a Windows update messes with the registry keys that point to those files, Word can't find them anymore. What you're seeing is a missing or corrupted MSSPELL.DLL or MSPPROOF.DLL file, or a broken registry path under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\Proofing Tools.

The error text is misleading—it says the check is "not installed." It's usually installed but not registered properly. The installer or an Office update left the files on disk but failed to write the correct registry entries, or the entries point to a language code that doesn't match the installed files.

The fix: repair Office or reinstall the language pack

There are two approaches. Try the quick one first—it works in about 60% of cases. If that doesn't do it, you'll need to mess with the Office installer directly.

Step 1: Run a Quick Repair (no internet needed)

1. Close all Office apps.
2. Press Win + R, type appwiz.cpl, hit Enter.
3. Find Microsoft Office (or Microsoft 365) in the list. Select it, click Change.
4. Choose Quick Repair, then Repair.
5. Wait for it to finish. It'll check the proofing tool registry keys and re-register the DLLs. Takes about 2 minutes.

Test with F7 in Word. If it still fails, move to Step 2.

Step 2: Online Repair (downloads fresh files)

1. Same as Step 1, but choose Online Repair. This reinstalls the full suite from Microsoft's servers. Make sure you have a stable internet connection.
2. After it finishes, reboot your machine. The installer should fix registry paths for proofing tools automatically.

Step 3: If the error persists, check your language pack

Sometimes you installed an Office language pack separately (e.g., French proofing on an English Office). That pack's files may have been removed by a Windows update or a disk cleanup. Here's how to reinstall just the proofing tools for that language:

1. Go to Settings > Time & Language > Language & region.
2. Under Preferred languages, click the three dots next to the language that Word's spell check is failing for (e.g., English (United States)). Choose Language options.
3. Scroll down to Keyboards and make sure at least one keyboard is installed. That's not the fix itself—it just forces Windows to keep the language installed.
4. Now open Word, go to File > Options > Language. Under Choose Editing Languages, ensure the language you need shows as Enabled. If it says Not Installed, click the link to install proofing tools.

If that link doesn't exist or does nothing, you can manually download the language pack from Microsoft's Language Accessory Pack page. Install it, reboot, and test again.

Step 4: Registry fix (advanced—only if above fails)

If you're comfortable editing the registry, the root of the problem is often a missing or wrong InstalledRoot or Language value. What you're looking for is the key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\Proofing Tools. Under there, subkeys named like 1033 (English) or 1036 (French) should exist and have a string value Root pointing to C:\Program Files\Common Files\Microsoft Shared\Proofing.

• If the entire Proofing Tools key is missing, that's your problem. A Quick Repair usually creates it.
• If the subkey for your language is missing (e.g., no 1033), then the proofing DLLs weren't registered. Run regsvr32 on MSSPELL.DLL and MSPPROOF.DLL from an admin command prompt. Both live in C:\Program Files\Common Files\Microsoft Shared\Proofing.

Don't edit the registry unless you're sure—a wrong key can break other Office tools.

What to check if it still fails

• Third-party antivirus: Some aggressive scanners (looking at you, McAfee and Norton) quarantine proofing DLLs because they look like keyloggers. Check your quarantine list and restore MSSPELL.DLL and MSPPROOF.DLL from C:\Program Files\Common Files\Microsoft Shared\Proofing.
• Corrupt user profile: Create a new Windows user account, log in, open Word, and test F7. If it works, your original user profile's registry hive is corrupted. Migrate your data—fighting that is a losing battle.
• Office version mismatch: If you have both the 32-bit and 64-bit versions of Office installed (rare but possible), the proofing tools from one version won't work with the other. Uninstall both and do a clean install of one architecture.

The real fix is almost always Step 1 or Step 2. If you're reading this on a helpdesk ticket and the user says "I already tried Quick Repair," ask if they rebooted after. The post-repair reboot is what finalizes the DLL registration—half the time the repair actually works, the user just didn't restart.