NHunspell - Free Spell-Checker, Hyphenation and Thesaurus for .NET

NHunspell is a spell checking, hyphenation, word stemming and thesaurus library based on Hunspell. NHunspell can use Open Office dictionaries for spell checking, hyphenation and thesaurus.

This is the new home of NHunspell. It is still free and open source, we moved it here to provide  better support. Please update your Bookmarks!

Spell Checker, Hyphenation and Thesaurus: NHunspell

NHunspell brings the spell checking, hyphenation and thesaurus to the Microsoft® .NET Framework. NHunspell is C# library and wraps native libraries for Hunspell, Hyphen and MyThes. One design goal of this library and wrapper is to keep the source code of the included libraries as unmodified as possible. New versions of the base libraries can therefore easily adopted to NHunspell. The integrated libraries are used in OpenOffice and they work with the dictionaries published on

Installation and Support

NuGet is the recommended installation method for NHunspell. You can also access and download the sourcecode.  If you have questions, suggestions or find a bug, please use the free support forum to inform us.

Here are the resources we provide for NHunspell:

If you miss something or need consulting or developement services, please feel free to contact us.


NHunspell is licensed under: GPL/LGPL/MPL. Free use in commercial applications is permitted according to the LGPL and MPL licenses. Your commercial application can link against the NHunspell DLLs.

Hunspell Dictionaries

The Hun­spell dic­tio­nar­ies are of­ten dis­trib­uted in pack­ages which are in fact Zip files. If you want to use them you must ex­tract the dic­tio­nar­ies. Hun­spell is used in many projects, there­fore the dic­tio­nar­ies are widely spread and it can be a mess to find the new­est ones. Below are web sites and di­rect links to Hun­spell dic­tio­nar­ies. Important: Dictionaries have a own license which may not be public domain. Check the dictionary license first before you use them. 


The spell checker Hun­spell needs two files:
Dic­tionary file with .DIC ex­ten­sion (e.g. en_us.dic)
Af­fix file with .AFF ex­ten­sion (e.g. en_us.aff)


The hy­phen­ator Hyphen needs one file:
Dic­tionary File with .DIC ex­ten­sion (e.g. hyph_en_us.dic)
To dis­tin­guish be­tween Hun­spell and Hyphen dic­tio­nar­ies, the Hyphen dic­tio­nary names start with 'hyph_' by con­ven­tion.


The the­saurus MyThes needs one file:
Data file with .DAT ex­ten­sion (e.g. th_en_us.dat)

Open Office Dictionaries

Dictionaries are distributed as Open Office Extension (.OXT). In fact the Open Of­fice ex­ten­sion files are Zip files. To get the dic­tio­nar­ies you must download and un­zip the .OXT file.

Open Office 3.x and above Dictionaries

Open Office 1.x and 2.x Dictionaries

Firefox Dictionaries

The Fire­fox add-ons (.XPI) are in fact Zip files. To get the dic­tio­nar­ies you must un­zip the .XPI file.

Firefox Dictionaries

Thunderbird Dictionaries

The Thun­der­bird add-ons (.XPI) are in fact Zip files. To get the dic­tio­nar­ies you must un­zip the .XPI file.

Thunderbird Dictionaries

NHunspell Components

NHunspell has four components: Spell checking, hyphenation thesaurus and a spell engine for high throughput multi-threaded spell checking.


The spell checker library Hunspell is a state of the art spell checker for languages with complex word compounding and rich morphology. It was written by László Németh for spell checking of the Hungarian language and can be used with utf8 encoded Unicode directories. Hunspell is based on MySpell and can use MySpell directories too.

Hunspell is the default spell checker of OpenOffice, Mozilla Thunderbird and Firefox, Google Chrome and the Apple MAC OS/X operating system since version 10.6 "Snow Leopard". Hunspell is based an MySpell and can use the MySpell dictionaries. It is an alternative to GNU Aspell, ISpell, PSpell and Enchant.


The hyphenation library Hyphen is part of the Hunspell project written by László Németh. It is a state of the art hyphenator.


MyThes is a managed thesaurus implementation it can use dictionaries form Open Office.

Spel­lEngine - Spell Check, Hyphen­ation and Th­e­saurus for Server and Web Server (ASP.NET)

Spel­lEngine al­lows the thread-safe ex­e­cu­tion of spell check re­quests. It is a com­po­nent opimzed for servers. All NHun­spell fea­tures (spell check, hy­phen­ation, the­saurus, anal­y­sis and gen­er­a­tion) are in­te­grated. To en­sure full uti­liza­tion of the CPUs on sev­eral re­quests, one Hun­spell, Hyphen or MyThes is in­stan­ti­ated per pro­ces­sor or pro­ces­sor core and con­trolled by a sem­a­phore. Mul­ti­ple dic­tio­nar­ies can be in­stalled to serve dif­fer­ent lan­guages. Spell check, hy­phen­ation, and syn­onyms in mul­ti­lin­gual ap­pli­ca­tions are sup­ported with­out any ad­di­tional pro­gram­ming.

Online Demo

A free on­line the­saurus, hy­phen­ator and spell checker was mad with the new Spel­lEngine. Please visit the home­page:

On­line Spell Check, Hyphen­ation and Th­e­saurus

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