How to Create and Customise Custom and Exclude Dictionaries in Microsoft Word

While Microsoft Word’s standard spelling checker boasts comprehensive vocabularies across English dialects and international languages, technical documentation and professional authoring often encounter unique proofing challenges. On one hand, specialised medical jargon, engineering terms, chemical compounds, and corporate brand names are repeatedly flagged with red squiggly underlines. On the other hand, certain words that are technically spelled correctly in general English (such as “manager” vs “manger”, “discrete” vs “discreet”, or obsolete spellings) slip past automated checks despite violating your organisation’s house style guide. Microsoft Word addresses both needs through Custom Dictionaries and Exclude Dictionaries.

The Roles of Custom vs Exclude Dictionaries

Understanding how Word evaluates user vocabularies alongside its primary dictionary clarifies the workflow:

• Custom Dictionaries (.dic files): Whitelists of words that are not found in the main dictionary. Adding terminology here stops Word from flagging proprietary acronyms, client names, or industry terms as spelling errors.
• Exclude Dictionaries (.lex files): Blacklists of words that are in the standard dictionary, but which you want Word to deliberately flag as incorrect. This prevents commonly confused homophones, forbidden slang, or out-of-date product names from appearing in client deliverables.

Step 1: Create and Manage a Custom Dictionary in Word

To establish a shared or project-specific dictionary for legal, medical, or technical terms:

1. Open Microsoft Word.
2. Click on the File tab in the upper-left corner and select Options.
3. In the Word Options dialogue box, click on Proofing in the left-hand navigation pane.
4. Under the section titled When correcting spelling in Microsoft Office programs, click the Custom Dictionaries… button.

Step 2: Add New Dictionaries and Import Word Lists

From the Custom Dictionaries manager:

1. Click the New… button to create a bespoke dictionary file (e.g., LegalTerms.dic or CorporateBranding.dic).
2. Save the file in the default Office proofing folder (typically %AppData%\Microsoft\UProof\).
3. Ensure the checkbox next to your new dictionary is ticked.
4. To add terms manually, select the dictionary and click Edit Word List….
5. Type your term in the Word(s): box (e.g., a proprietary framework or client name) and click Add.
6. Click OK to save your additions.

Because .dic files are plain UTF-16 text files with one word per line, you can also open them directly in Notepad to paste bulk terminology lists from company glossaries.

Step 3: What is an Exclude Dictionary and Where Does It Live?

Unlike Custom Dictionaries, which have a dedicated button in Word Options, Exclude Dictionaries are pre-linked system files tied to specific language codes. Microsoft Office creates an empty exclude dictionary file for each installed language pack inside your user profile directory:

C:\Users\[Username]\AppData\Roaming\Microsoft\UProof\

Identifying Your Language Code Lexicon

The exclude file uses the naming format ExcludeDictionary[LanguageCode].lex. Common language codes include:

• ExcludeDictionaryEN0809.lex: English (United Kingdom) – LCID 2057 / Hex 0809
• ExcludeDictionaryEN0409.lex: English (United States) – LCID 1033 / Hex 0409
• ExcludeDictionaryEN0c09.lex: English (Australia) – LCID 3081 / Hex 0c09
• ExcludeDictionaryEN1009.lex: English (Canada) – LCID 4105 / Hex 1009

Step 4: Customise Your Exclude Dictionary to Flag Forbidden Words

To force Word to flag words that violate house rules:

1. Close Microsoft Word completely.
2. Press Windows Key + R on your keyboard to open the Run dialogue box.
3. Type %AppData%\Microsoft\UProof and press Enter. File Explorer will open directly to your proofing directory.
4. Locate the file matching your language dialect (for example, ExcludeDictionaryEN0809.lex for UK English). If the file does not exist, right-click, choose New > Text Document, and rename it with the .lex extension.
5. Right-click the .lex file and open it with Notepad.
6. Add the specific words you wish Word to flag as misspelled, typing one word per line in all lowercase letters:

   theatre
   judgement
   furthermore
   synergy

7. Save the file as Unicode (UTF-16 LE) and close Notepad.

Step 5: Test and Verify the Exclude Rule in Word

Relaunch Microsoft Word and type the excluded words into a blank document:

1. Word will immediately draw a red wavy underline beneath the excluded words, treating them as spelling errors even though they exist in standard dictionaries.
2. Right-clicking the flagged word presents standard suggested corrections or highlights the term for review, ensuring no restricted words make it into final publication.

Troubleshooting Custom and Exclude Dictionaries

• Exclude Dictionary Not Flagging Words: Ensure that the text language of your paragraph matches the language code of the .lex file. If your text is tagged as English (US) but you edited ExcludeDictionaryEN0809.lex (UK), Word will not apply the rule. Select your document text and verify the language in Review > Language > Set Proofing Language.
• Encoding Corruption: Always save .lex files with Unicode or UTF-16 LE encoding. Saving as plain ASCII or ANSI may cause Word to ignore the file entirely.
• Sharing Dictionaries Across an Organization: System administrators can deploy standardised .dic and .lex files across enterprise workstations via Group Policy Objects (GPO) or Microsoft Intune by copying the files directly to %AppData%\Microsoft\UProof\.