Modern Online JSON Formatter, Validator & Beautifier
JSONGuy is a modern JSON formatter that pretty-prints and validates JSON in your browser — with syntax highlighting and a collapsible tree view. Supports JSON5, JavaScript-style JSON, and Python objects (comments, single quotes, unquoted keys, trailing commas, None/True/False). 100% client-side, no sign-up required.
Click Beautify to format your JSON.
More JSON tools
JSON Beautifier
Pretty-print raw or compact JSON with 2 or 4 space indentation, GitHub-style syntax highlighting, and a collapsible tree view for easy navigation.
JSON Validator
Live validation catches syntax errors instantly and reports the exact line and column, so you can fix broken JSON in seconds.
JSON5 & Python Object Syntax
Paste JSON5, modern JavaScript-style JSON, or a Python dict — unquoted keys, single quotes, trailing commas, comments, and None/True/False — and normalize it into strict, standards-compliant JSON.
Accepts more than JSON
Most tools only take strict JSON. JSONGuy handles the syntax people actually write — and normalizes it all into clean, standards-compliant JSON.
JSON5 & JS objects
{
name: 'John', // comment
skills: ['js', 'react',],
}Unquoted keys, single quotes, comments, and trailing commas.
Python dicts
{
'active': True,
'nickname': None,
'tags': ('a', 'b'),
}None/True/False and tuples are converted to JSON equivalents.
Broken JSON
{
name: John,
city: New York
}Missing quotes and commas get repaired automatically.
From any AI client
Connect the MCP server and let your agent format, validate, or repair JSON without leaving the conversation.
Learn more →Frequently Asked Questions
What is a JSON formatter?
A JSON formatter takes raw or compact JSON and reformats it with indentation and line breaks so it is easy to read. JSONGuy also validates the structure and highlights syntax errors with their exact line and column.
How do I format JSON online?
Paste your JSON into the input box and click the Beautify button between the two panes. JSONGuy pretty-prints the JSON in the output pane, and you can use the tree view to navigate nested objects and arrays.
Can I format JSON5, JavaScript-style JSON, or Python objects?
Yes. JSONGuy supports JSON5 and relaxed JavaScript object syntax — unquoted keys, single-quoted strings, trailing commas, and line or block comments — plus Python dicts with None, True, and False. It normalizes all of them into standard JSON.
How do I validate JSON?
Click Validate, or rely on the live status bar at the bottom of the tool. Invalid input is reported immediately with the error message and the offending line and column.
Is my JSON data sent to a server?
No. All formatting and validation runs locally in your browser. Your JSON is never uploaded or stored on a server.
What makes JSONGuy a modern JSON formatter?
Unlike legacy formatters, JSONGuy is built for modern development. It understands JSON5, JavaScript-style JSON, and Python objects (unquoted keys, single quotes, trailing commas, comments, None/True/False), offers GitHub-style syntax highlighting, a collapsible tree view, live validation, and runs entirely in your browser with no server round-trips.
Does JSONGuy have an MCP server?
Yes. Connect JSONGuy's formatter, validator, and repair tools to Claude, Cursor, or any MCP client. It accepts the same inputs as the web tool — JSON, JSON5, JavaScript objects, and Python dicts — and can repair broken JSON. Learn more about JSONGuy.