Is there a standard or specification defining json file extensions?
I saw .json used - is it just common practice or is it a requirement of some standard for json saved in file format?
.json
According to the Douglas Crockford project, the JSON format is found here :
"The JSON parser converts the JSON text to another representation.The JSON parser MUST accept all texts that match the JSON grammar. The JSON parser MAY take forms other than JSON or Extensions. "
So this is just common practice; as long as your file matches the JSON grammar, the extension does not have to be * .json (although it may be useful for you and other developers, if any).