JSON (JavaScript Object Notation) is a lightweight text format for storing and exchanging structured data. It uses human-readable key-value pairs, arrays, and nested objects. JSON is language-independent — almost every programming language has libraries to parse and generate it. It is the dominant data format for REST APIs, configuration files, and NoSQL databases like MongoDB.

How do I validate JSON?

Paste your JSON into the formatter above — any syntax error is highlighted with the line number and a description of the problem. Common JSON errors include: trailing commas (not allowed in JSON, unlike JavaScript), single-quoted strings (JSON requires double quotes), unquoted keys, and missing closing brackets or braces. The formatter shows valid JSON reformatted with proper indentation.

What is the difference between pretty-printing and minifying JSON?

Pretty-printing (formatting) adds indentation and newlines to make JSON human-readable — useful for debugging, documentation, or reviewing API responses. Minifying removes all unnecessary whitespace to produce the smallest possible string — useful for HTTP responses and storage where every byte counts. Both representations parse to the same data structure.

What is the difference between JSON and XML?

Both are text formats for structured data, but JSON is generally preferred for web APIs because it is more compact, directly parseable in JavaScript without conversion, and easier to read. XML offers advantages in some enterprise contexts: it supports comments (JSON does not), has well-established schemas (XSD), and is better suited for document markup. For new REST APIs, JSON is the standard choice.

What are the most common JSON syntax errors?

The five most common: (1) Trailing comma after the last item in an array or object — valid in JavaScript but not in JSON. (2) Single-quoted strings — JSON requires double quotes for all strings and keys. (3) Unquoted object keys — JavaScript allows unquoted keys, JSON does not. (4) Comments — JSON does not support // or /* */ comments. (5) undefined values — JSON supports null, but not JavaScript's undefined.

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