JSON Formatter, Validator & Beautifier
This free online JSON formatter helps you format, validate, beautify, and minify JSON data instantly in your browser. Paste raw or messy JSON, choose an output style, and get clean, readable results you can copy or download. Nothing is uploaded to a server — all processing happens locally, so it is safe to use with private and sensitive data.
JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format that is easy for humans to read and write and easy for machines to parse and generate. It has become the de facto standard for REST APIs, configuration files, and data exchange between web and mobile applications. JSON is built from objects (unordered collections of "key": value pairs wrapped in curly braces) and arrays (ordered lists wrapped in square brackets); values can be strings, numbers, booleans, null, objects, or arrays.
How to use JSON Formatter
- Paste your JSON into the Input box.
- Choose a format type: Pretty (Indented), Compact (Minified), Single Line (Spaced), NDJSON, or TOON.
- For indented formats, pick an indent size (2 or 4 spaces are the most common).
- Optionally enable "Sort Object Keys Alphabetically" for deterministic, diff-friendly output.
- Press Process. The formatter validates your JSON and shows the exact parser error if something is wrong.
- Copy the result or download it with a file extension matching the chosen format.
Why format and validate JSON?
Minified or hand-edited JSON is hard to read and easy to break. Formatting (also called pretty-printing or beautifying) adds consistent indentation and line breaks so the structure is obvious at a glance, which makes debugging APIs and reviewing configuration files far faster. Validation catches syntax errors — such as trailing commas, single quotes, or missing brackets — before they reach production. This tool validates as it formats and shows the exact parser error when something is wrong.
{
"name": "Ada Lovelace",
"age": 36,
"active": true,
"roles": ["admin", "author"]
}Output formats explained
Choose the output that fits your workflow. Here is what each format option produces and when to use it.
Pretty (Indented)
The classic beautified format. Each nested level is indented (1–8 spaces, controlled by the Indent Size slider) with one key or element per line. Best for reading, debugging, code reviews, and committing readable config files to source control.
Compact (Minified)
Removes all optional whitespace to produce the smallest valid JSON on a single line — for example {"a":1,"b":[1,2,3]}. Use it to shrink API payloads, embed JSON in environment variables, or reduce file size and bandwidth.
Single Line (Spaced)
Collapses the JSON onto one line but keeps a space after each colon and comma — {"a": 1, "b": [1, 2, 3]}. It is more readable than the fully minified Compact output while still fitting on a single line, which is handy for logs, spreadsheet cells, and inline documentation.
NDJSON (Newline-Delimited JSON)
Converts a JSON array into newline-delimited JSON, writing one compact JSON object per line. This streaming-friendly format is widely used for logs, data pipelines, and bulk import APIs (such as Elasticsearch and BigQuery). NDJSON requires the input to be a JSON array.
TOON (Token-Oriented Object Notation)
A compact, human-readable encoding of the JSON data model designed to minimize tokens when sending structured data to large language models (LLMs). TOON expresses uniform arrays of objects as a compact table with the field names declared once, which can dramatically reduce token usage compared with equivalent JSON while remaining lossless.
users[2]{id,name,role}:
1,Alice,admin
2,Bob,userFormatting options
- Indent Size: choose 1–8 spaces per level for the Pretty and TOON formats. Two and four spaces are the most common conventions.
- Sort Object Keys Alphabetically: recursively reorders every object's keys in alphabetical order, producing deterministic output that is ideal for diffing two JSON documents or normalizing configuration files.
Related terminology
- Pretty-printing
- Reformatting data with indentation and line breaks so its structure is easy to read; the opposite of minification.
- Minification
- Removing all optional whitespace from JSON to make the payload as small as possible without changing the data.
- NDJSON
- Newline-delimited JSON — one complete JSON value per line, used for streaming and log processing.
- TOON
- Token-Oriented Object Notation, a lossless, token-efficient encoding of the JSON data model designed for LLM prompts.
- JSON Schema
- A vocabulary for describing and validating the shape of JSON documents (types, required keys, value constraints).
Frequently asked questions
- What is a JSON formatter?
- A JSON formatter is a free online tool that takes raw or minified JSON and rewrites it into a clean, consistent, human-readable layout. It parses your input, validates that the syntax is correct, and lets you re-serialize it as pretty-printed, compact, single-line, NDJSON, or TOON output. Everything runs locally in your browser, so your data never leaves your device.
- How do I format (beautify) JSON online?
- Paste your JSON into the input box, choose the "Pretty (Indented)" format, pick an indent size (2 or 4 spaces are the most common), and press Process. The formatter validates your JSON and outputs an indented, easy-to-read version that you can copy or download.
- What does minifying JSON do?
- Minifying (the "Compact" option) removes every non-essential space and line break, producing the smallest possible valid JSON on a single line. This reduces payload size for APIs, configuration files, and network requests without changing the underlying data.
- Is my JSON data sent to a server?
- No. This JSON formatter runs entirely in your browser using client-side JavaScript. Your JSON is never uploaded, stored, or transmitted, which makes it safe for sensitive or proprietary data.
- What is TOON format?
- TOON (Token-Oriented Object Notation) is a compact, human-readable encoding of the JSON data model designed to minimize tokens when passing structured data to large language models (LLMs). It represents uniform arrays of objects as a compact table, and can use significantly fewer tokens than equivalent JSON while remaining lossless.
- Why is my JSON invalid?
- Common causes of invalid JSON include trailing commas, single quotes instead of double quotes, unquoted object keys, missing brackets or braces, and comments (which JSON does not allow). This tool reports the exact parser error message so you can locate and fix the problem quickly.