Calwarden

Online JSON Beautifier

Prettify or Minify JSON data.

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Calculator

Inputs

Paste the JSON object or array you want to format.

Choose readable indentation or compact output.

Live output

Results

Formatted JSON
{
  "id": 1,
  "name": "Product",
  "features": [
    "A",
    "B"
  ]
}

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Document

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Assumptions

  • The input must be standard JSON, so keys and string values need double quotes and comments are not supported.
  • Prettify uses a fixed 2-space indentation style for readable output.
  • Minify removes non-essential whitespace without changing the underlying JSON data.

Sensitivity preview

No numeric sensitivity scenarios are available.

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About this JSON Formatter

JSON (JavaScript Object Notation) is the language of the web APIs. However, raw JSON often comes back as a single unreadable line of text. This tool formats ('prettifies') that text into a structured, easy-to-read layout, or compresses ('minifies') it for efficiency.

Who this calculator is for

  • Frontend developers inspecting API responses, fixtures, or config blobs during debugging.
  • QA teams and support staff validating whether copied payloads are valid before sharing them.
  • Anyone cleaning JSON for documentation, issue reports, or lightweight data handoffs.

When to use it

  • Prettify a minified API response before reading nested objects and arrays.
  • Minify a valid JSON payload before embedding it in a request body, env var, or test fixture.
  • Quickly confirm whether pasted JSON is valid before using it in code or tooling.

How to use this calculator

  1. Paste your JSON string into the Input box.
  2. Select Prettify to indent and format the code.
  3. Select Minify to remove whitespace and reduce size.
  4. The result appears instantly in the output box.

Key assumptions

  • The input must be standard JSON, so keys and string values need double quotes and comments are not supported.
  • Prettify uses a fixed 2-space indentation style for readable output.
  • Minify removes non-essential whitespace without changing the underlying JSON data.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

The tool uses JavaScript's native `JSON.parse()` to validate the structure and `JSON.stringify()` to reformat it. It runs entirely in your browser—no data is sent to a server.

Understanding your results

If the input is invalid (e.g., missing a comma or quote), the tool will display an error message explaining exactly what went wrong.

Key Features

  • Syntax Validation
  • 2-Space Indentation
  • Error Highlighting

Glossary of Terms

JSON
JavaScript Object Notation. A lightweight data-interchange format.
Minification
The process of removing all unnecessary characters from source code without changing its functionality.
Parse Error
An error returned when the syntax of the JSON string violates the standard rules.

Frequently Asked Questions

Is my JSON data sent to a server?
No. This tool processes your JSON entirely within your web browser using JavaScript. No data leaves your device.
Why does it say my JSON is invalid?
JSON is strict about syntax. Common errors include using single quotes instead of double quotes for keys/strings, trailing commas, or missing brackets.
What is the difference between Prettify and Minify?
Prettify adds indentation and newlines to make the data human-readable. Minify removes all unnecessary whitespace to reduce the file size for storage or transmission.
Can comments be used in JSON?
Standard JSON does not support comments. If your data includes comments (like // or /* */), the parser will throw an error.
How do I handle dates in JSON?
JSON does not have a native Date type. Dates are typically stored as ISO 8601 strings (e.g., '2023-10-27T10:00:00Z') and must be parsed by the application consuming the data.