JSON does not define a precision for numbers, so: it's often float64 (but note -0 is allowed, but NaN and +/-Inf are not), but it depends on your language, par

JSON does not define a precision for numbers, so: it's often float64 (but note -0 is allowed, but NaN and +/-Inf are not), but it depends on your language, parser config, etc. Many will produce higher precision but parse as float64 by default. But maximally-compatible JSON systems should always handle arbitrary precision.