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Using correct spelling improves your communication and can prevent costly mistakes and even lethal mistakes. Several solutions have been developed over the last decades, each building on top of the previous one. The current state of affairs is that there is a need for a fast, transparent and maintainable spelling checker.

To meet these demands, the free and open source spelling checker Nuspell is being created. Its aim is to be integrated in mainstream office suites, web browsers, email clients, computer-assisted translation services and other applications working with text. Speed, accuracy, documentation and maintainability are the main advantages that put Nuspell at the front of contemporary spell checking solutions.



Familiar examples of both proprietary or open source software which can start using Nuspell as a drop-in replacement of their current spelling checker are:

Also web services, lesser-known text editors and more technical software such as IDEs can use Nuspell. Integration can be done in many ways such as dynamic linking or static linking, but Nuspell can be integrated via language bindings too.


Main features of Nuspell spelling checker:

  • Provides software library and command-line tool.
  • Suggests high-quality spelling corrections.
  • Backward compatibility with Hunspell dictionary file format.
  • Up to 3 times faster than Hunspell.
  • Full Unicode support backed by ICU.
  • Twofold affix stripping (for agglutinative languages, like Azeri, Basque, Estonian, Finnish, Hungarian, Turkish, etc.).
  • Supports complex compounds (for example, Hungarian, German and Dutch).
  • Supports advanced features, for example: special casing rules (Turkish dotted i or German sharp s), conditional affixes, circumfixes, fogemorphemes, forbidden words, pseudoroots and homonyms.
  • Free and open source software. Licensed under GNU LGPL v3 or later.

Furthermore, Nuspell has:

  • a C++17 library licensed to prevent vendor lock-in
  • an extensive testing framework and CI to optimize functionality and performance
  • documented code and algorithms promoting transparency, understanding and maintenance
  • ports and packages for at least all major operating systems and distributions, including:
    • Linux
    • macOS
    • Windows
    • BSD

Character encodings encountered in dictionaries and affix files which Nuspell works are at least:

Languages and Users

Currently, almost 90 different languages and language variations are supported. This covers the languages used in almost 200 countries and geographic regions in the world. As many users can also use a second language, such as English, the user base is almost all of the approximately 2.5 billion computer users. That is a third of the Earth’s population.

Nuspell itself does not support any language. You need language support, also called a language pack or dictionary, in order for Nuspell to check spelling in a certain language. Language support can be found for:

Note that installing language support is automated and directly available from inside the software listed above.


Our wiki has a page with an extensive listing of binary packages to easily install Nuspell.


Even though spell checking can be a very complex subject, we need your help. Nuspell isn’t simply using a list of correct words, but a mechanism of very intricate spelling checker techniques and tactics. Nevertheless, we can use help on all levels from fixing bugs, implement feature requests, improving support for a certain language, porting to platforms, packaging for operating systems and integrating browsers and office suites.

To help keep a healthy community and promote diversity and inclusion, we work with a code of conduct. Contact us if you can contribute with your skills and learn more about spelling checkers.


Several organizations have enabled the development and maintenance of Nuspell. The sponsors, past and current, are:

Contact us if you are considering sponsoring the development and maintenance of this free and open source spelling checker. Especially with so many users and many different software integrations, this software is in constant need of proficient support. Reducing spelling errors not only improves quality of communication and indirectly teaches people about spelling, but it also reduces the risk for costly errors that could have been prevented.


The code, wiki and issues are managed at GitHub. Use that repository, also the closed issues, for any questions or contributions. Find Nuspell also on social media.


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