Correct, JSON can handle any precision, because it's just dumped as a string anyway, just not enclosed in the "". However, as you mentioned, as soon as it comes through the parser it'll put it into an underlying float value. In C# I create a save high precision attribute that will take the value and put it directly into a decimal. In JS I'm sure there's some way to do that, but that parser is way less extensible compared to C#. However, this also all assumes you know the client will parse it correctly, overriding the default behavior. Safest is to just send it as a string, and then create your parsers to automatically send to and from strings