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The JSON "Number" standard is arbitrary precision decimal[1], though it does mention that implementations MAY limit the parsed value to fit within the allowable

The JSON "Number" standard is arbitrary precision decimal[1], though it does mention that implementations MAY limit the parsed value to fit within the allowable range of an IEEE 754 double-precision binary floating point value. JSON "Number"s can't encode all JS numbers, since they can't encode NANs and infinities. [1] https://www.ecma-international.org/wp-content/uploads/ECMA-404_2nd_edition_december_2017.pdf https://www.ecma-international.org/wp-content/uploads/ECMA-4... section 8.

WorldMaker 4y ago
The "dual" standard RFC 8259 [1] (both are normative standards under their respective bodies, ECMA and IETF) is also a useful comparison here. It's wording is a bit stronger than ECMA's, though not by much. ("Good interoperability" is its specific call out.) It's also interesting that the proposed JSON 5 (standalone) specification [2] doesn't seem to address it at all (but does add back in the other IEEE 754 numbers that ECMA 404 and RFC 8259 exclude from JSON; +/-Infinity and +/-NaN). It both maintains that its numbers are "arbitrary precision" but also requires these few IEEE 754 features, which may be even more confusing than either ECMA 404 or RFC 8259. [1] https://datatracker.ietf.org/doc/html/rfc8259#section-6 https://datatracker.ietf.org/doc/html/rfc8259#section-6 [2] https://spec.json5.org/#numbers https://spec.json5.org/#numbers