Question

I’ve seen so many complicated questions in SO whether or not some complicated structure is considered to be valid JSON.

But what about something on the other end of the spectrum?

"12345"

Is the above valid JSON?

Answer 1

Yes, in most contexts. It is valid JSON syntax representing a JSON value.

The confusion around this comes from Douglas Crockford’s RFC 4627, which originally defined the application/json internet media type in 2006. It said that:

A JSON text is a serialized object or array.

However, as Crockford explained in a post in 2013 (unfortunately deleted with rest of Google+, but archived here):

JSON is just a grammar, and the grammar includes numbers and strings. Uses of JSON must necessarily be more restrictive. RFC-4627 is one possible use, and was never intended to be the standard for JSON itself.

The example string is a valid JSON value, but it would have been incorrect to use it as the full "JSON text" body of an application/json HTTP response. However, that’s no longer true: RFC-4627 was obsoleted in 2014 with the publication of RFC 7159, which lets you use any JSON value:

A JSON text is a serialized value. Note that certain previous specifications of JSON constrained a JSON text to be an object or an array.

A "standard for JSON itself" was also published in 2013, as ECMA-404, and JSON was also defined in edition 5.1 of the ECMAScript (JavaScript) specification ECMA-262. These specifications and most parsers allow any JSON value as a complete JSON text, even if it’s just a simple string.