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JSON
JSON Tools FAQ — Formatting, Validation & Conversion
Answers to the most common questions about JSON formatting, validation, minification, and conversion. Learn what JSON is, when to minify it, and how to fix common errors.
Q1 What is JSON?
JSON (JavaScript Object Notation) is a lightweight, text-based data format used to exchange data between systems. It stores data as key-value pairs and arrays, making it both human-readable and easy for machines to parse. Example:
{"name": "Alice", "age": 30, "active": true}. JSON is the standard format for REST APIs, configuration files, and database documents (MongoDB, Firestore).
Q2 How do I validate JSON online?
Paste your JSON into the JSON Formatter tool and click "Format". If the JSON is valid, it will be pretty-printed with indentation. If invalid, you'll see an error message pointing to the exact line and character that caused the problem. Common errors include trailing commas, single quotes instead of double quotes, and unquoted keys.
Q3 Why minify JSON?
Minification removes all whitespace, newlines, and indentation from JSON, reducing its size by 15–30%. This speeds up network transfers when sending JSON in API responses or embedding it in web pages. Use the JSON Formatter to minify with one click. In production, always minify JSON payloads; keep formatted versions for development and debugging.
Q4 What is the difference between JSON and JavaScript objects?
JSON and JavaScript objects look similar but have key differences. In JSON: all keys must be double-quoted strings, values can only be strings, numbers, booleans, null, arrays, or objects — no functions or undefined. JavaScript objects can use unquoted keys, single quotes, and any value type including functions. Example difference:
JSON: {"key": "value"} vs JS: {key: 'value', fn: () => {}}.
Q5 How do I fix 'Unexpected token' JSON errors?
The most common causes of JSON parse errors are: (1) trailing commas after the last item in an array or object — JSON forbids them; (2) single quotes used instead of double quotes; (3) unquoted property keys; (4) comments — JSON does not support comments; (5) undefined or NaN values. Use the JSON Formatter to highlight exactly where the error is.
Q6 How do I convert JSON to CSV?
Use the JSON to CSV Converter. Paste a JSON array of objects — the tool automatically uses the object keys as CSV column headers. Download the result as a .csv file or copy it directly into Excel or Google Sheets. Best for flat JSON arrays; deeply nested structures may need flattening first.
Q7 What is the difference between JSON and XML?
JSON is more concise, faster to parse, and natively supported in JavaScript. XML supports attributes, namespaces, and schemas, making it better for document-centric data and legacy enterprise systems. A JSON record takes roughly 30–40% fewer characters than equivalent XML. Modern REST APIs almost universally use JSON; XML remains common in SOAP web services, RSS feeds, and SVG.
Q8 How do I pretty-print JSON in Python?
Use Python's built-in
json module: import json; print(json.dumps(data, indent=2)). To format a JSON string: print(json.dumps(json.loads(json_string), indent=2)). For quick one-off formatting without writing code, use the online JSON Formatter.
Q9 Is JSON case-sensitive?
Yes, JSON keys are case-sensitive.
{"Name": "Alice"} and {"name": "Alice"} are different keys. The JSON specification (RFC 8259) does not enforce unique keys, but most parsers use the last value for duplicate keys. Always use consistent casing — lowercase with underscores (snake_case) or camelCase are the two common conventions.
Q10 What is JSON Lines (JSONL)?
JSON Lines (also called JSONL or newline-delimited JSON) is a format where each line is a separate, valid JSON object. It's used for streaming data, log files, and large dataset exports because you can process it line by line without loading the entire file into memory. Example:
{"id":1,"name":"Alice"} on line 1, {"id":2,"name":"Bob"} on line 2.
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