OnlineDeveloperTool
JSON Tools

JSON Formatter Online

Paste messy or minified JSON, get clean, indented JSON back. Then copy it with one click.

Updated

Ctrl/Cmd + Enter to run

Formatting changes whitespace only. JavaScript parsing can change very large integer precision, collapse duplicate keys, or reorder integer-like keys, so keep the original input when exact preservation matters.

This tool runs in your browser. No account or signup is required.

Common JSON Formatter tasks

Developers typically reach for this page when they need to format minified json; make json readable online; format json with indentation. The tool is built for quick, practical work rather than a generic demo.

What matters in a json formatter workflow

When developers compare online tools for this job, the useful capabilities tend to center on custom indentation, exact error location, file input, tree view, privacy. This page keeps those practical needs in mind while linking to related tools when a different workflow is a better fit.

What is JSON Formatter?

JSON Formatter (also called a JSON beautifier or pretty printer) takes a JSON string and re-prints it with 2-space indentation so you can actually read it.

What problem does it solve?

API responses, config files and log lines often arrive as one unreadable line. Formatting by hand is slow and error-prone, and a missing comma is easy to miss.

How to use JSON Formatter

  1. Paste your JSON into the input box.
  2. Press Process.
  3. Copy the formatted result. If the JSON is invalid, you get the parser error instead.

Example

Input

{"name":"Ada","tags":["dev","math"]}

Output

{
  "name": "Ada",
  "tags": [
    "dev",
    "math"
  ]
}

What you can do with JSON Formatter

  • Format JSON online
  • Pretty print JSON
  • Beautify minified JSON

Common use cases

  • Reading a minified API response
  • Cleaning up a JSON config before committing it
  • Making a payload readable for a bug report

Related developer tasks

  • Format JSON online
  • Pretty print JSON
  • Beautify minified JSON

Common JSON errors and how to fix them

If the formatter shows an error, the input is not strict JSON. These are the usual causes:

  • A trailing comma after the last item in an object or array. Remove it.
  • Single quotes around keys or strings. JSON requires double quotes.
  • Unquoted keys such as {name: "Ada"}. Every key must be a double-quoted string.
  • Comments (// or /* */). JSON has no comment syntax, so strip them first.
  • Values such as undefined, NaN or Infinity. None of these exist in JSON; use null or a string.
  • Raw line breaks or unescaped quotes inside a string. Write them as \n and \".

What formatting changes, and what it does not

Formatting normally changes whitespace, but the parser and serializer can also normalize some values. Very large integers can lose precision, duplicate object keys keep only the last value, and integer-like keys can be reordered.

Because it uses JavaScript's parser, three behaviors are worth knowing. Integers larger than 9,007,199,254,740,991 lose precision. If an object repeats a key, the last value wins and the earlier one is dropped. Keys that look like whole numbers, such as "1" or "2", are moved to the front in ascending order.

Where a JSON formatter helps most

  • Reading API responses and webhook payloads copied from logs or a network panel
  • Reviewing config files such as package.json or appsettings.json
  • Making request bodies readable in bug reports and documentation
  • Spotting a missing bracket before it reaches production

Next steps: JSON Validator, JSON Beautifier, JSON Minifier, JSON to C#

JSON Formatter FAQ

What makes JSON invalid?

Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, and comments. Strict JSON allows none of these.

Does formatting preserve my JSON exactly?

Formatting changes whitespace, but this tool uses JavaScript JSON.parse and JSON.stringify. Very large integers can lose precision, duplicate object keys keep only the last value, and integer-like keys can be reordered. Keep the original input when exact preservation matters.

Is my data sent to a server?

The processing runs in your browser, so what you paste into the tool is not uploaded for processing. As with any tool, avoid pasting live secrets you cannot afford to leak.

What is the difference between a JSON formatter and a JSON validator?

A formatter re-prints valid JSON with indentation. A validator only tells you whether the JSON is valid. This formatter also shows the parser error when the JSON is invalid, so it checks syntax as a side effect.

Can I choose tabs or 4-space indentation?

Yes. The formatter supports 2 spaces, 4 spaces or tabs. JSON validity is unchanged; only the output whitespace differs.

Can it format very large JSON files?

It runs in your browser's memory, so inputs of many megabytes can be slow or freeze the tab. For very large files, a command-line tool such as jq is a better fit.

Looking for something else? Browse all developer tools.

onlinedevelopertool.com is a collection of 54 free, browser-based utilities for the small jobs that interrupt real work: formatting a JSON response, decoding a token, converting a timestamp, generating a UUID or checking a hash. Each tool has its own page with a short explanation, a worked example and answers to common questions, so you can use it and learn what it does at the same time.

There is no account to create and nothing to install. Tools run in your browser, so the text you paste is processed on your own device. The one exception is the Website Status Checker, which sends a request from your browser to the address you enter.

Three steps: paste your input, click the tool, copy the result, all inside your browser
Popular developer utilities: JWT decoder, UUID generator, Base64 decoder, SHA-256 hash, regex tester and timestamp converter

What you can do here

  • JSON Tools

    Format, validate, beautify and minify JSON, generate C#, TypeScript, Java, Python, Go, PHP and Kotlin models from it, or convert between JSON, YAML and CSV.

  • Encoders & Decoders

    URL, Base64 and HTML encoding and decoding, plus a JWT decoder for reading token claims.

  • Generators & Hashes

    Generate UUIDs and JWTs, validate UUIDs, and create MD5, SHA-256 and SHA-512 hashes.

  • Web Tools

    Timestamps, color codes, query strings and cron expressions - the small things web work keeps throwing at you.

  • Text & Data

    Format XML and YAML, count text, change case, make slugs, test regex, diff two texts and convert number bases.

  • Website Checking

    Check whether a website or URL is reachable from your browser.

Quick developer reference

  • JSON

    Keys and strings must use double quotes, and trailing commas and comments are not allowed. Those are the three most common reasons a payload fails to parse.

    Validate JSON

  • JWT

    A JSON Web Token is three Base64URL parts joined by dots: header, payload and signature. Decoding shows the claims but does not prove the token is genuine; only signature verification does.

    Decode a JWT

  • Base64

    Base64 is an encoding, not encryption. Anyone can reverse it, and it makes data roughly one third larger, so never use it to hide secrets.

    Decode Base64

  • UUID

    A version 4 UUID is made of random bits and written as 8-4-4-4-12 hexadecimal characters. Collisions are astronomically unlikely, which is why they work well as identifiers.

    Generate a UUID

  • Timestamps

    A Unix timestamp counts time since 1 January 1970 UTC. Ten digits usually means seconds and thirteen digits usually means milliseconds.

    Convert a timestamp

  • Hashes

    MD5 is fine for quick checksums but is not safe for security. Prefer SHA-256 or SHA-512, and remember that hashing is one-way and is not encryption.

    Create a SHA-256 hash

Missing a tool you need? Visit the contact page and tell us what you reach for most often. You can also browse every tool or read the About page to see how the site is built and what it does with your data.