Office Settings & Configuration

What Is the Maximum Size of a Microsoft Word Custom Dictionary?

Natalie Taylor Oct 1, 2026 869 views

Question details

The user wants to know the word-count or file-size limit for a custom dictionary in Microsoft Word.

What Is the Maximum Size of a Microsoft Word Custom Dictionary?

Product: Microsoft Word
Device & OS: not provided
Scenario: Adding specialized vocabulary to Word's spell-checker and managing custom dictionary files without causing performance issues.
Observed behavior: Seeking clarification on the maximum capacity of the custom dictionary text file to prevent errors or application slowdowns when adding numerous new words.

Before you start

To manage your proofing tools effectively, locate your current custom dictionary file (usually named CUSTOM.DIC) and ensure you have access to the Word Options menu.

Solution 1Recommended

Managing Custom Dictionary Size and Performance in Word

Since Microsoft Word does not have a strict word-count limit for custom dictionaries, managing file size and utilizing multiple dictionaries is the best practice.

Microsoft does not publish a separate, fixed word-count limit for custom dictionaries in Word. Because a custom dictionary is stored as a standard plain-text file (.dic), its practical size depends entirely on your file system, available system storage, and Word's general text-handling capabilities.

However, to ensure optimal spell-check performance and prevent the application from slowing down, it is highly recommended to keep the dictionary file well below Word's general 32 MB file-size limit for text-only documents.

Use multiple custom dictionaries

Instead of storing thousands of terms in a single massive file, navigate to File > Options > Proofing and click on Custom Dictionaries. From here, you can create and add multiple smaller dictionaries categorized by subject, such as medical, legal, or technical terms.

Maintain plain-text formatting

If you are editing the dictionary file directly in a text editor like Notepad, ensure you save it strictly as a plain-text file. Adding rich text formatting or special characters can corrupt the file and cause spell-check failures.

Edit words directly through settings

To safely modify your dictionary without risking file corruption, go to File > Options > Proofing > Custom Dictionaries, select your dictionary, and click 'Edit Word List'. You can safely add or delete individual words from this dialog.

Managing Custom Dictionary Size and Performance in Word

Importing Third-Party Dictionaries: You can easily import third-party custom dictionaries downloaded from the internet and use them alongside your default dictionary to instantly expand your recognized vocabulary.

Free Microsoft Office alternative

Try WPS Office for Seamless Word Processing and Proofing

If you are managing complex dictionary setups or looking for a lightweight, reliable word processor, WPS Office is an excellent free alternative to Microsoft Word. It provides a familiar interface, robust built-in spell checking, and complete file compatibility.

1. Download and Install WPS Office: Visit the official WPS website to download the free suite and install it on your computer.
2. Open Your Document: Launch WPS Writer and open your existing Word documents. The formatting and layout will remain perfectly intact.
3. Utilize Spell Check: Navigate to the Review tab on the top ribbon and click Spell Check to utilize the built-in proofing tools.

100% free and lightweight installationFully compatible with Microsoft Word formats (.doc, .docx)Built-in spell check with support for custom dictionariesFamiliar user interface requires zero learning curve

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Frequently Asked Questions

Where is the custom dictionary file located in Windows?

By default, the custom dictionary file (CUSTOM.DIC) is usually located in the AppData folder. You can navigate to C:\Users\[YourUsername]\AppData\Roaming\Microsoft\UProof to find it.

Why are words in my custom dictionary still being marked as misspelled?

This usually happens if the custom dictionary is unchecked in the Custom Dictionaries dialog box, or if the dictionary's assigned language does not match the proofing language of the text in your document.

Can I share my custom dictionary with another computer?

Yes, you can copy the CUSTOM.DIC file from your current computer, transfer it to another machine via a USB drive or email, and then add it through Word's Proofing settings by selecting 'Add' in the Custom Dictionaries menu.

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