Microsoft has an okay Finnish spellchecker. It's really a shame no Finnish university has developed an acceptable open source Finnish spellchecker though AFAIK.

Microsoft has an okay Finnish spellchecker. It's really a shame no Finnish university has developed an acceptable open source Finnish spellchecker though AFAIK. Word-list based checkers actually work for English, which gives an impression that they would work for all types of languages. For agglutinative languages (which I think is about 50% of world languages) not so much, since the list of valid words is basically infinite. But combined with a high-quality root word list it's possible to write a computer program that returns if a given input word is a valid form of some known root word, i.e. a spellchecker. In English, you can think the problem same as writing a spellchecker that can tell if an input word is a valid chemical name for a molecule, like 1,3,7-trimethylxanthine (caffeine) or adenosine-5'-triphosphate (ATP). Clearly, we can not write an exhaustive list of valid words here. But it's pretty easy to write a computer program that can tell if the input word at least seems like a valid chemical name devoid of typos.