JSON uses true, false and null

Why True, False and None cause a JSON parse error, and how to get valid JSON out of Python instead of a printed dictionary.

Open the JSON formatter

What the error looks like

Different engines word this differently. You may see any of these:

SyntaxError: Unexpected token T in JSON at position N
SyntaxError: JSON.parse: unexpected character at line N column N of the JSON data

Why it happens

JSON's three literals are lowercase: true, false and null. They are case sensitive.
Python spells them True, False and None, and printing a dictionary produces Python syntax, not JSON.
The give-away is that the same document usually has single quotes too, because it is the repr of a dict rather than serialised JSON.

Example

Invalid

{'active': True, 'deleted': False, 'note': None}

Valid

{"active": true, "deleted": false, "note": null}

How this tool reports it

The formatter corrects all three literals and the surrounding single quotes together, so a pasted Python dictionary becomes valid JSON in one pass.

Paste your JSON into the formatter to see the exact line and column, or use the validator if you only need to check it.

Worth knowing

In Python use json.dumps(value) rather than print(value) or str(value). The latter two produce a repr, which only coincidentally resembles JSON.