.LEX File Extension

File Type 1

Adobe Linguistic Library Data File

Developer Adobe Systems
4.0  |  30 Votes
Category Data Files
Format Binary

What is a LEX file?

A LEX file is a lexicon data file created by Linguistic Library, an Adobe development kit used to add linguistic services, such as spelling and grammar checkers, to Adobe products. It contains the shared lexicons, or words and their syntax, for a language. LEX files are used to store language-specific data for document validation in Adobe products.

More Information

LEX files can be used across multiple Adobe products, including Acrobat, Photoshop, InDesign, and Illustrator.

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Programs that open or reference LEX files

Adobe Linguistic Library
Adobe Linguistic Library
Updated December 18, 2018
File Type 2

Spelling Dictionary File

Developer Microsoft
3.5  |  2 Votes
Category System Files
Format Text and Binary

A LEX file may also be a spelling dictionary used by Microsoft Windows, Microsoft Office, and other Microsoft programs. It contains a wordlist that is used to spell check users' text and provide spelling suggestions. LEX files are not meant to be opened or edited.

More Information

By default, Windows includes a number of LEX files that are used as spelling dictionaries for different languages. For example, in Windows 10, the file MsSp7en-US.lex is used as the primary U.S. English spelling dictionary. A number of other LEX files can be found in sub-directories of the C:/​Windows directory.

LEX files are primarily binary files, which means they cannot be opened, viewed, or edited in a text editor. So, you cannot easily view or edit the dictionary a LEX file contains. Extremely savvy users may be able to create their own exclusion dictionary to accompany a LEX dictionary, allowing them to "edit" the dictionary. Novices should not attempt to create an exclusion dictionary.

NOTE: LEX files are different than custom Microsoft Office dictionaries, which are saved as .DIC files.

How to open a LEX file

LEX files are not meant to be opened or edited. If you want to create and use a custom Microsoft Office dictionary, open an Office application and select Options → Proofing → Custom Dictionaries....

Programs that open or reference LEX files

Updated June 2, 2021

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