OpenTaal ("Open Language") is a Dutch foundation which provides free Dutch language files to be used in open-source software spell checking, hyphenation, thesaurus and grammar checking.[1][2][3]

Formation1 November 2005; 15 years ago (2005-11-01)
TypeNon-profit organization
Legal statusFoundation
PurposeProviding software assisting proper use of Dutch language


In 1996 a working group of the Dutch TeX User's Group created a word list for spell checking and hyphenation to be used in TeX software. This list is also used in and has been developed since. At the end of 2005 the Dutch Language Union (Nederlandse Taalunie), the formal Dutch language institute, published a new version of the "Woordenlijst Nederlandse Taal" (Dutch Language Word list, also known as "the Green Booklet"). The new spelling rules laid down in it are compulsory in government and education of participating countries since August, 2006. To comply with the spelling changes, the existing free language files had to be adjusted. At the same time, the opportunity arose to have them certified by the Dutch Language Union. The OpenTaal project was founded to facilitate the collaboration of open source projects in this area.


Spell checkingEdit

OpenTaal provides files for spelling check which are being used in software such as, Firefox,[4] Thunderbird,[5] Safari, Opera, TinyMCE and more. Some of this software receives custom files from OpenTaal while other software uses the generic spelling checker Hunspell. This is using its own custom file from OpenTaal. Even the Dutch Wiktionary[6] uses this list of correctly spelled words.

Word listEdit

The Dutch Language Union[7] has approved OpenTaal's word list and labelled it with Keurmerk Spelling. Also OpenTaal has been granted funding by the Dutch Language Union to implement missing functionality in Hunspell.


A thesaurus has been set up in which many different relations between words and meaning of words can be browsed and edited.[8]

Grammar checkingEdit

OpenTaal also provides grammar rules which are used in the grammar checker LanguageTool. This is offering grammar checking via its own website[9] but is also used by and Thunderbird.[10] This grammar checker also identifies possible false friends.[11]


Since 2012, OpenTaal has an official program for partners.[12] These are third parties which have access to special partner products. From these collaborations the following has come forth. One partner has provided Dutch support for Wordfeud[13] and another partner has made an educational poster on diacritical marks in the Dutch language.[14]


  1. ^ "English". Retrieved October 27, 2019.
  2. ^ "Nieuwsberichten | Taalunieversum". Retrieved October 27, 2019.
  3. ^ "Nieuwsberichten | Taalunieversum". Retrieved October 27, 2019.
  4. ^ Dutch Dictionary add-on for Firefox
  5. ^ Dutch Dictionary add-on for Thunderbird
  6. ^ "WikiWoordenboek:OpenTaal - WikiWoordenboek". Retrieved October 27, 2019.
  7. ^ "Niet gevonden | Taalunieversum". Retrieved October 27, 2019.
  8. ^
  9. ^ LanguageTool Community on-line Dutch grammar checker
  10. ^ Grammar Checker add-on for Thunderbird
  11. ^ Dutch False friends which are supported by LanguageTool
  12. ^ "Vrienden van OpenTaal". Retrieved October 27, 2019.
  13. ^ (in Dutch) Taaltik - Wordfeud-woorden
  14. ^ (in Dutch) Sander van Geloven, Diakritische tekens in het Nederlands Archived 2013-10-29 at the Wayback Machine, educatieve poster, Hellebaard, Utrecht, 2012.

External linksEdit