JSON (JavaScript Object Notation) is a lightweight, text-based data-interchange format. It is easy for humans to read and write and easy for machines to parse and generate. It is built on two structures: a collection of name/value pairs (an 'object' or 'dictionary') and an ordered list of values (an 'array' or 'list').

What is JSON used for?

JSON is the *de facto* standard for data transfer in web applications. It's used almost everywhere: 1) **APIs:** Transmitting data between a server and a web or mobile application. 2) **Configuration Files:** Storing settings for applications (.json files). 3) **NoSQL Databases:** Storing documents in databases like MongoDB.

What is the most common JSON syntax error?

The two most common JSON syntax errors are: 1) **Missing Quotes on Keys:** In JSON, *all* keys (names) *must* be enclosed in double quotes (e.g., `"name": "value"`). JavaScript objects allow unquoted keys, but JSON does not. 2) **Trailing Commas:** A comma (`,`) after the last item in an object or array is *not allowed* in the JSON standard.

What is the difference between JSON and XML?

Both are used to exchange data. JSON is generally preferred today because it is: 1) **Less verbose** (it doesn't use closing tags). 2) **Easier to parse** for machines. 3) It maps *natively* to JavaScript objects. XML is still widely used in enterprise systems, SOAP APIs, and document-centric formats.

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What is JSON? (Formatter & Validator Guide)

**JSON (JavaScript Object Notation)** is a lightweight, text-based data format. It has become the *de facto* standard for data transmission in web APIs, replacing older formats like XML.

It is built on two simple, universal data structures:

A collection of **key/value pairs** (e.g., an `object`, `dictionary`).
An ordered list of **values** (e.g., an `array`).

Why Use a JSON Formatter & Validator?
Humans and machines have different needs. Machines prefer **minified JSON** (all whitespace removed) to save bandwidth. Humans need **formatted/beautified JSON** (with indentation and line breaks) to read and debug.

**Formatter/Beautifier:** This tool takes unreadable, minified JSON and adds indentation to make it "pretty-printed" and human-readable.
**Validator:** JSON has a very strict syntax. A single missing quote or an extra comma will make it invalid. This tool acts as a **JSON validator** by parsing the text. If it formats successfully, your JSON is valid. If it fails, it will highlight the exact line with the **syntax error**.
**Minifier:** This tool also does the reverse, taking a beautified JSON and "minifying" (or "uglifying") it by removing all whitespace, making it as small as possible for production use.

JSON Formatting Examples

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JSON Syntax Rules & Common Errors

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Error: Keys Must Have Double Quotes

This is the most common error for JavaScript developers. In a JS object, {name: "John"} is valid. In JSON, it is **invalid**. The key *must* also be in double quotes: {"name": "John"}. All strings, both keys and values, use double quotes.

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Error: No Trailing Commas

Another common syntax error. A comma (`,`) is not allowed after the *last* element in an array or the *last* property in an object.
{"a":1, "b":2,} ← **Invalid.**
{"a":1, "b":2} ← **Valid.**

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JSON vs. JavaScript Objects

JSON is a **string data format**, *based on* JS object syntax. It is **not** a JS object. JSON cannot contain functions, `undefined`, comments, or variables. It only supports objects, arrays, strings, numbers, booleans (true/false), and null.