Large-scale n-gram models are available for a small number of languages. So far, Croatian was not one of them. The research presented in this paper describes the development of n-gram database system suitable for large-scale language modeling in Croatian. The process of n-gram collection relies on Croatian academic online spellchecker Hascheck, which has been publicly available since 1993, and is today a popular language service, with average daily traffic exceeding million tokens. The approach demonstrated in this paper eliminated the need of n-gram data cleaning in the post-processing phase, which is a serious issue in other languages. The spellchecker dynamics allowed Heaps’ law modeling to be applied to Croatian n-grams, which enabled the prediction of n-gram count growth.