The Microsoft Common Speller API (CSAPI) for Office spell checking


The Microsoft Common Speller Application Programming Interface (CSAPI) is a standardized set of functions that allows host applications to better communicate with external spell checkers and lexicons (dictionaries). This standardization allows for the development of third-party engines and lexicons that can be sold in the market place as add-ins for Microsoft Office. These add-ins provide Office users with the ability to customize and extend the capabilities of Office spell checking.

To facilitate development of a new engine and lexicon, Microsoft has made the CSAPI specification available. Third parties that are interested in implementing only an add-in lexicon (such as medical, legal, or technical terms) but not an engine only require specific tools to convert their lexicon into the appropriate format and should be aware that this is only supported for English and CSAPI is not required.

Developers who are interested in implementing a CSAPI spell check engine and lexicon, or only an add-in lexicon, can contact Microsoft Developer Support. The following Microsoft Knowledge Base article contains the contact information:
234322 Getting support for Microsoft Office Solutions

Note CSAPI may not be used to call into Microsoft's spell check engine and lexicon. For example, third-party developers who want to incorporate spell check capabilities into their own applications may not use CSAPI to access the spell check engine and lexicons that are installed by Microsoft Office. Microsoft does not currently provide spell check utilities for use in third-party products.

More Information

The CSAPI documentation and the lexicon tools are provided to developers who want to build their own custom spell check engine and/or lexicon. They are provided upon written request and are not supported by Microsoft Technical Support. The documentation is informational only.

Developers who want to add spell checking to their custom application can contact one of the following vendors to obtain a spell check engine and development license:
Wintertree Software Sentry and WSpell Spelling Checkers

ComponentOne VSSPELL (formerly VideoSoft VSSPELL)

BeCubed AZSpell (formerly HighSpell)
NOTE: The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.


Developers who are working within Office who need spell check capabilities can use the automation model of the Office application to do spell checking for them.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

243844 How to automate Word from Visual Basic or from Visual Basic for Applications for spell checking