JSON Formatter and Validator

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python dict to json

Convert a Python dict to JSON (single quotes, True, False and None)

Paste the dictionary the way Python printed it and turn repair on. The output is strict JSON, and the list of changes shows every quote and value swapped, with the exact column, so you can check before applying.

Why a printed dict is not JSON

When you print() or repr() a Python dictionary, the result is the object representation in Python syntax, not a data interchange format. The differences from JSON are few and systematic: strings come out in single quotes, while JSON requires double quotes; booleans are written True and False with a capital initial, and JSON uses lowercase true and false; the null value is None, and JSON uses null. Tuples come out in parentheses, which JSON does not have, and special float values such as nan and inf have no equivalent either.
The formatter repair swaps single quotes for double ones and rewrites any double quote that was inside the text, converts True, False and None, and turns NaN and Infinity into null, because JSON represents neither. It also handles the curly quotes that appear when the dictionary goes through a word processor or a chat. What repair does not do is guess types that Python has and JSON does not, such as dates, Decimal, sets or bytes: if the print shows something like datetime.datetime(2026, 1, 5), the text stays outside the grammar and the error list points to the spot so you can decide the representation, for example an ISO 8601 string.
If you control the Python code, the right path is to skip the print: json.dumps(data) produces strict JSON, and json.dumps(data, indent=2, ensure_ascii=False) already comes out formatted and with readable accents. One quirk of Python json module is that, by default, it writes NaN and Infinity when it meets those floats, which produces text that other parsers reject; pass allow_nan=False to fail early. When the data was already printed and only the log is left, the repair here handles the case safely, and the order of the dictionary keys is kept.

Checked conversions

Python boolean and null

Input: {'ativo': True, 'chefe': None}
Expected output: {"ativo":true,"chefe":null}

Four changes: two quotes and two values.

Strings and list

Input: {'nome': 'Ana', 'tags': ['a', 'b']}
Expected output: {"nome":"Ana","tags":["a","b"]}

Five single-quoted strings become double-quoted.

Python NaN

Input: {'x': NaN}
Expected output: {"x":null}

JSON has no NaN, so it becomes null.

Curly quotes from a word processor

Input: {“nome”: “Ana”}
Expected output: {"nome":"Ana"}

Curly quotes become straight.

Leading zero

Input: {"a": 007}
Expected output: {"a":"007"}

Becomes a string so the zeros are not lost.

Full tool FAQ

Why does my JSON give "Unexpected token" and where is the error?

The most common causes are a comma after the last item, single quotes, an unquoted key, a comment, and a missing comma between two values. JSON.parse reports only the first problem and, in some browsers, only a character position. This formatter lists every error in the text, each with line and column, shows the snippet with an arrow under the exact spot, marks the line in the editor margin, and has a Go to the error button that selects the spot.

Can JSON have comments or a trailing comma?

Do single quotes work in JSON? What about a Python dict?

What does Repair mode do and what are its limits?

What happens when the JSON has the same key twice?

Why does a big number change after going through JavaScript?

Does sorting keys or minifying change what the JSON means?

How do I validate a JSON Lines or NDJSON file?

Which query syntax is supported?

Is my JSON sent to any server? What about large files?

Frequently asked questions

How do I convert a Python dict to JSON in code?

Use json.dumps(data) from the standard library json module. With indent=2 it comes out formatted, with ensure_ascii=False accents stay readable, and with allow_nan=False the code fails if it meets NaN or Infinity instead of producing invalid JSON.

Why does Python print single quotes?

The repr of a string picks single quotes by default, and only uses double quotes when the text already contains a single quote. It is a Python convention for displaying objects, unrelated to the JSON format.

Do dates, Decimal and sets work in repair?

No. Those types do not exist in JSON and their repr is not a syntax that repair can read safely. The error list shows where they are, and you swap them for an ISO 8601 string, a number or a list.

Does repair change the order of keys?

No. Keys come out in the original order unless you choose Sort keys. Python dictionaries keep insertion order since version 3.7, and that order is preserved.

Next steps

Why a printed dict is not JSON

When you print() or repr() a Python dictionary, the result is the object representation in Python syntax, not a data interchange format. The differences from JSON are few and systematic: strings come out in single quotes, while JSON requires double quotes; booleans are written True and False with a capital initial, and JSON uses lowercase true and false; the null value is None, and JSON uses null. Tuples come out in parentheses, which JSON does not have, and special float values such as nan and inf have no equivalent either.

The formatter repair swaps single quotes for double ones and rewrites any double quote that was inside the text, converts True, False and None, and turns NaN and Infinity into null, because JSON represents neither. It also handles the curly quotes that appear when the dictionary goes through a word processor or a chat. What repair does not do is guess types that Python has and JSON does not, such as dates, Decimal, sets or bytes: if the print shows something like datetime.datetime(2026, 1, 5), the text stays outside the grammar and the error list points to the spot so you can decide the representation, for example an ISO 8601 string.

If you control the Python code, the right path is to skip the print: json.dumps(data) produces strict JSON, and json.dumps(data, indent=2, ensure_ascii=False) already comes out formatted and with readable accents. One quirk of Python json module is that, by default, it writes NaN and Infinity when it meets those floats, which produces text that other parsers reject; pass allow_nan=False to fail early. When the data was already printed and only the log is left, the repair here handles the case safely, and the order of the dictionary keys is kept.

Checked conversions

Python boolean and null

Input: {'ativo': True, 'chefe': None}
Expected output: {"ativo":true,"chefe":null}

Four changes: two quotes and two values.

Strings and list

Input: {'nome': 'Ana', 'tags': ['a', 'b']}
Expected output: {"nome":"Ana","tags":["a","b"]}

Five single-quoted strings become double-quoted.

Python NaN

Input: {'x': NaN}
Expected output: {"x":null}

JSON has no NaN, so it becomes null.

Curly quotes from a word processor

Input: {“nome”: “Ana”}
Expected output: {"nome":"Ana"}

Curly quotes become straight.

Leading zero

Input: {"a": 007}
Expected output: {"a":"007"}

Becomes a string so the zeros are not lost.

Full tool FAQ

Why does my JSON give "Unexpected token" and where is the error?

Can JSON have comments or a trailing comma?

Do single quotes work in JSON? What about a Python dict?

What does Repair mode do and what are its limits?

What happens when the JSON has the same key twice?

Why does a big number change after going through JavaScript?

Does sorting keys or minifying change what the JSON means?

How do I validate a JSON Lines or NDJSON file?

Which query syntax is supported?

Is my JSON sent to any server? What about large files?

Frequently asked questions

How do I convert a Python dict to JSON in code?

Why does Python print single quotes?

Do dates, Decimal and sets work in repair?

No. Those types do not exist in JSON and their repr is not a syntax that repair can read safely. The error list shows where they are, and you swap them for an ISO 8601 string, a number or a list.

Does repair change the order of keys?

No. Keys come out in the original order unless you choose Sort keys. Python dictionaries keep insertion order since version 3.7, and that order is preserved.