WALS is great! A warning though: the individual data points aren’t always completely reliable. I regularly attempt to track down specific language features list

WALS is great! A warning though: the individual data points aren’t always completely reliable. I regularly attempt to track down specific language features listed in WALS only to find that half of them don’t correspond to what’s in the source (which to be fair is quite characteristic of big linguistic databases). That being said, the overall geographic trends in the maps are still pretty reliable, and the accompanying ‘chapters’ [https://wals.info/chapter https://wals.info/chapter] are amongst the best free linguistic resources I’ve yet found. From the same group, there’s also https://glottolog.org/ https://glottolog.org/ for general information about language families, and https://clics.clld.org/ https://clics.clld.org/ for lexicon organisation. All these are part of a broader set of linked datasets listed at https://clld.org/datasets.html https://clld.org/datasets.html (I’ve found PHOIBLE particularly interesting, which collects phonological information). Again, the same provisos apply: generally helpful on average, but take specific data points with a grain of salt.