Cysill Online (2009) is a free online tool for Welsh grammar and spell checking. Based on the commercial Cysill grammar and spell checking programme, part of the Cysgliad (2004) software package for Windows, it is limited to checking texts with a length of approximately 3000 characters. As stated in the Terms of Use, submitted texts are stored as a corpus for academic research purposes and are a useful source of word frequency counts, neologisms, common errors, dialectal forms and named entities. The corpus is not publicly available due to issues of confidentiality. However, an anonymized subset is available as part of our Example Corpus of Language Registers.