1. Jonathan Snook at 3:44am on August 8, 2006

Just to clarify a couple things that even confused me about JSON.  Despite calling it "object notation", the ECMA spec never uses the term. The object literal is the term the spec uses. Hey, I've used the term object notation, too, as the equivilant of object literal.

That issue aside, the reason for double quotes and not single quotes likely has to do with language support. For example, valid JSON is valid JavaScript is valid Python. In most other languages, double quotes are used to denote strings. There's a definite consistency in sticking with double quotes.

2. Jesse Skinner at 10:11am on August 8, 2006

Yeah, the language support thing makes sense now. The "object notation" thing threw me off too even as I was writing this article - I added the word "literal" afterwards because I wasn't even aware I should be using the word.

3. Terr at 9:38pm on August 10, 2007

Also, suppose you have a JSON string in PHP or some other language, and you want to put the string as the value in an HTML form element. When constructing the (x)HTML and the value attribute of the input tag, do you single-quote the JSON? Do you double-quote it? Do you know in advance whether the string you are about to put between quotes has it's own internal quotes which will make for broken HTML?

Having "double quoted only" is very wise because then nobody has to constantly guess or convert, and you can print the JSON string into the HTML and reliably use single quotes around it.

4. Jesse Skinner at 5:58am on March 6, 2008

@Terr - That's actually rather dangerous. You should be using addslashes() or a similar function to escape single quotes when placing a JSON string inside single quotes.

Consider the following valid JSON example:

var json = '{ "key": "this's the value" }';

As you can see, the single quote inside the string will cause a syntax error.

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