Single Quotes in JSON: Why They're Invalid

Quick answer: JSON allows double quotes only — every key and every string value must be wrapped in ". Single quotes (') are invalid, even though JavaScript and Python accept them, so JSON.parse() rejects them. To fix it, replace the single quotes with double quotes. The JSON Trimmer converts single-quoted JSON5-style input into strict JSON automatically.

This looks like JSON but isn't:

{'name': 'Dana', 'role': 'admin'}

The keys and values use '. Strict JSON requires:

{"name": "Dana", "role": "admin"}

The error you'll see is typically Unexpected token ' in JSON (or, in newer engines, a message saying property names must be double-quoted strings), with the position pointing at the first single quote.

JSON's grammar was kept deliberately tiny so that every parser in every language agrees on what's valid. Allowing both quote styles would add ambiguity for no benefit, so the spec (RFC 8259) permits exactly one: the double quote. This is the same minimalism that forbids trailing commas and comments.

The confusion comes from neighboring languages:

• JavaScript object literals accept 'single', "double", and `backtick` strings.
• Python dictionaries print with single quotes by default (str(my_dict)), which is not JSON.

So code that's perfectly valid in a .js file or a Python REPL becomes invalid the moment it's treated as JSON.

• Quickly: paste it into the JSON Trimmer, which normalizes single quotes (and other JSON5 extras) to strict, double-quoted JSON.
• In Python: never build JSON with str(dict) or print(dict). Use json.dumps(), which always emits double quotes:

import json
data = {"name": "Dana", "role": "admin"}
json.dumps(data)   # '{"name": "Dana", "role": "admin"}'

• In JavaScript: generate JSON with JSON.stringify() rather than writing object literals by hand — it always double-quotes keys and strings. See Parse and Stringify.

A double-quoted string can contain an apostrophe with no escaping needed:

{"note": "it's fine"}

You only need to escape a " that appears inside a double-quoted string (as \"). For the full rules on quotes and escapes, see Escaping Special Characters. After converting, validate with the JSON Validator to be sure nothing else is off.

Can JSON use single quotes? No. JSON requires double quotes for all keys and string values. Single quotes always cause a parse error.

Why does my Python dictionary look like JSON but won't parse? Printing a dict (str(dict)) uses single quotes and Python literals like True/None, which aren't valid JSON. Use json.dumps() to produce real JSON.

How do I convert single quotes to double quotes safely? Don't do a blind find-and-replace — apostrophes inside values would break. Use a JSON5-aware tool like the JSON Trimmer, or re-serialize the data with your language's JSON encoder.

Do I need to escape apostrophes in JSON? No. An apostrophe inside a double-quoted string is just a normal character. Only the double quote and backslash need escaping inside a string.