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What's the difference between Sentry and WSpell?

Wintertree Software has two spellcheck products for Windows developers: Sentry Spelling Checker Engine and WSpell ActiveX Spell Checker. Understandably, we are often asked which product best suits a customer's requirements.

Should I use Sentry Spell Checker or WSpell?

Sentry and WSpell are both first-class spellcheckers. WSpell uses the Sentry spell check engine internally, so each product offers similar spellchecking capabilities, including speed, options, dictionaries, suggestions, etc. However, there are some differences between the two products, as outlined in the following table:


Sentry Spell Checker

WSpell ActiveX Spell Checker

Application interface

Applications call functions in the Sentry API.

Applications set properties, call methods, and catch events.

Spell check "As you type"

Yes. Sentry can mark misspelled words typed into rich-text boxes. Sentry includes a feature that will remove the marks applied to misspelled words in a document on request from your application.

Yes. WSpell can mark misspelled words typed into rich-text boxes. Please note that WSpell does not support a feature to remove the marks applied to misspelled words.

Spell check in Web page forms

Sentry can be used in ASP applications to check the spelling of text entered in HTML forms (however, Wintertree Spelling Server is a better choice for this purpose).

Supported in Internet Explorer 3 and later. See Using WSpell to check text in Web pages in Internet Explorer for more information.


32 bit DLL.

32-bit ActiveX control (OCX).

Development environment

Can be used from any development environment that supports calling DLLs. We recommend Sentry if you develop using C, C++, C#, MFC, VB.NET, Delphi, Microsoft Access, Paradox, or other languages/tools such as PowerBuilder, Oracle Forms, etc.

Requires an ActiveX control container. Different control containers work in different ways; WSpell does not work with all of them. We recommend using (and have tested) WSpell with Visual Basic and Internet Explorer 3 and later.

Run-time redistribution requirements

Self-contained DLL (about 220K) plus dictionaries (about 350K)

OCX (about 180K) requires possible installation of several Microsoft DLLs (common to all MFC ActiveX controls) on the target system (only if they are not already installed or have incompatible versions), plus dictionaries (about 350K).

Source code availability

Available as a separate product.

Not available.

Cross-platform support

Source code is compilable on any platform which supports an ANSI C compiler, including UNIX and Macintosh.

Win32 (Intel) only (Win9x, NT, 2000, XP, etc.).


Alternate dialog templates and strings can be provided at run time.

Custom dialogs must be written. Example source code showing how to do this in Visual Basic is included.

Word list compression

Includes utility programs to turn a word list in text form into a compressed dictionary.

Not included.

.NET support

Yes. Sentry can be used in C# and VB.NET Windows Forms applications.

While WSpell can be used in .NET applications, we recommend Sentry instead.

Other points:

WSpell is an ActiveX control. ActiveX controls are easy to use in well-implemented control containers such as Visual Basic. In some circumstances, ActiveX controls introduce more complications than do simple DLLs such as those included with the Sentry Windows SDK. For example, ActiveX controls must be registered on the target system. Problems that arise with registering can be difficult to diagnose unless you are very familiar with ActiveX technology.

WSpell uses the ActiveX licensing protocol. Most control containers (including Visual Basic and Internet Explorer) correctly implement this protocol. Some control containers (e.g., some versions of PowerBuilder) do not implement the licensing protocol correctly. MFC implements the protocol when you use the ActiveX control in a dialog box. If you use WSpell in non-interactive situations, your application is responsible for implementing the licensing protocol. If you create an ActiveX control which itself uses WSpell, your control is also responsible for implementing the licensing protocol.

The DLLs included with the Sentry Windows SDK are built the same way as the DLLs which form the Windows API. This means they can be used in any programming language/development environment that permits calling the Windows API. Generally, DLLs result in fewer software development headaches than to ActiveX controls.

The bottom line: We recommend WSpell for VB and IE developers. We recommend Sentry for developers who use all other programming languages.

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