Is the JSON sent to a server?

No. All processing happens in your browser — your JSON never leaves your device.

Does it validate JSON?

Yes. Invalid JSON shows a clear error message with the exact line and column.

What is the keyboard shortcut?

Press Ctrl+Enter (or Cmd+Enter on Mac) to format JSON instantly.

Can it handle large JSON files?

Yes, the formatter handles large JSON files efficiently since processing is done natively in your browser.

What is the difference between JSON and JSON5?

JSON5 is a superset that allows comments, trailing commas, single-quoted strings, unquoted keys and hexadecimal numbers. Strict JSON (RFC 8259) forbids all of these, so a JSON5 document will not parse with a standard JSON.parse() call.

Why does my JSON fail to parse with a trailing comma?

Unlike JavaScript object literals, the JSON grammar (RFC 8259) does not permit a comma after the final array element or object member. Remove the trailing comma, or use a JSON5 parser if you need that flexibility.

Can a JSON object have duplicate keys?

The JSON spec leaves the behaviour undefined, so it is unsafe. Most parsers, including JavaScript JSON.parse(), silently keep the last value and discard earlier duplicates, which can hide bugs. This formatter can surface them so you fix the source.

Is there a JSON tree viewer?

Yes. After formatting, switch to the Tree view to explore nested objects and arrays with collapsible nodes — the same idea as a dedicated JSON viewer, but nothing is uploaded; the whole document is parsed and rendered in your browser.

What JSONPath syntax does the filter support?

A practical subset: the root ($), dot and bracket property access ($.a.b or $["a"]), array indices including negatives ($.items[0], $.items[-1]) and wildcards over arrays or object values ($.users[*].name, $.*). It is not the full JSONPath spec — there are no filter expressions or recursive descent — but it covers most everyday field extraction.

JSON Formatter & Validator

How to use JSON Formatter & Validator

The JSON Formatter, Validator and Viewer parses raw JSON, pinpoints syntax errors down to the exact line and column, and reformats the output with 2 or 4-space indentation. Switch to the collapsible tree view to explore a large payload like a JSON viewer, or filter it with a JSONPath expression. Developers use it to inspect API responses, debug configuration files and verify a payload is valid before committing.

Paste your JSON, or click Upload to load a .json file — nothing leaves your browser.
Choose 2 or 4-space indentation, and optionally Sort keys.
Click Format to see the prettified, colour-coded output, or an error with its exact line and column.
Switch to the Tree view to explore nested data, or type a JSONPath filter to narrow it down.
Copy the result or download it as a .json file.

Your data never leaves your device — 100% private processing.

Why JSON validation matters

A single misplaced comma or unquoted key causes an entire JSON document to be unparseable. Modern APIs return minified JSON that is impossible to read without formatting. Validators catch issues such as trailing commas (disallowed in JSON), single-quoted strings (only double quotes are valid), unescaped control characters and duplicate keys that silently overwrite earlier values.

JSON data types and structure

JSON supports six data types: string (double-quoted), number (integer or float), boolean (true/false), null, array (ordered list in square brackets) and object (key-value pairs in curly braces). Keys must be strings. Nested objects and arrays can go arbitrarily deep. The JSON Schema standard adds optional type validation and constraints on top of basic JSON structure.

JSON data types
Type	Example	Notes
string	"hello"	Must use double quotes
number	42 or 3.14	No NaN or Infinity
boolean	true / false	Lowercase only
null	null	Represents absence of value
array	[1, 2, 3]	Ordered, mixed types allowed
object	{"key": "value"}	Unordered key-value pairs

Worked examples

Pretty-print minified JSON

Inputs: {"a":1,"b":[2,3]}

Result: 2-space indented, 6 lines, keys aligned

Trailing comma flagged

Inputs: {"a":1,}

Result: Error: unexpected "}" — trailing comma not allowed in JSON

Minify back to one line

Inputs: formatted object across 6 lines

Result: {"a":1,"b":[2,3]}

Glossary

JSON: JavaScript Object Notation — a lightweight text format for data interchange.
Minification: Removing whitespace and newlines to reduce JSON file size for network transfer.
Schema: A JSON document that defines valid structure and data types for another JSON document.
Serialization: Converting a data structure to a string representation for storage or transmission.
Pretty-print: Reformatting JSON with indentation and newlines for human readability.

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JSON Formatter & Validator

How to use JSON Formatter & Validator

Why JSON validation matters

JSON data types and structure

Worked examples

Glossary

Related reading

Frequently Asked Questions

Why use JSON Formatter & Validator?

Common use cases

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