Question 1

How do I format JSON online?

Accepted Answer

Paste JSON into the input panel. The formatter parses it and pretty-prints valid input with two-space indentation. Invalid input shows the browser parser's error message. Formatting happens as you type.

Question 2

What does a JSON formatter do?

Accepted Answer

A JSON formatter takes compact JSON and adds indentation and line breaks for reading. This tool also reports syntax errors from JSON.parse; it does not highlight individual tokens or repair invalid JSON.

Question 3

Why is my JSON invalid?

Accepted Answer

Common errors include trailing commas, single-quoted strings, unquoted keys, comments, undefined, NaN, and Infinity. The formatter displays the browser's parser message, whose position detail varies by browser.

Question 4

What is valid JSON syntax?

Accepted Answer

Valid JSON requires double-quoted string keys and values, no trailing commas, no comments, and values must be strings, numbers, booleans (true/false), null, arrays, or objects. Single quotes, JavaScript-style comments (//, /* */), and undefined are all invalid in JSON.

Question 5

How do I minify JSON?

Accepted Answer

Use the dedicated JSON Minifier to parse JSON and emit a compact representation. It reports the raw UTF-8 size before and after; actual savings depend on the input and HTTP compression.

Question 6

What is the difference between JSON and a JavaScript object?

Accepted Answer

JSON is a data interchange format with stricter rules than JavaScript object literals. JSON requires double-quoted keys, forbids trailing commas, comments, functions, undefined, and Date objects. Use JSON.parse() to convert a JSON string to a JS object and JSON.stringify() to go the other way.

Question 7

What is the difference between JSON and JSONC?

Accepted Answer

JSONC (JSON with Comments) allows // and /* */ comments, used in VS Code settings files and tsconfig.json. Standard JSON (RFC 8259) forbids all comments — any parser will reject them. This formatter validates strict JSON. For JSONC, strip comments first. JSON5 is another superset allowing comments, trailing commas, and unquoted keys — useful for config files but not API payloads.

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