Free JSON prettifier

JSON prettifier

What the JSON prettifier does

Paste JSON in any state, one giant minified line, inconsistently indented, or copied out of a terminal with the formatting stripped, and this JSON prettifier parses it and hands back a version with two-space indentation and one value per line, so the nesting is visible at a glance.

It runs in your browser. Nothing you paste is sent anywhere, there is no signup, and there is no cap on how much JSON you format. Most of the well known formatters do not tell you where your data goes. This one does: it goes nowhere.

Why it matters

Why pretty-printed JSON is easier to read than one long line

A minified API response is often a single unbroken line, sometimes tens of thousands of characters long. Reading it means scanning left to right through braces and brackets with nothing to anchor on, trying to hold in your head which closing brace belongs to which opening one.

Reformatted with indentation, the same data reads the way code reads. Depth is visible from the indentation alone, and finding one key is a matter of looking down the left edge rather than counting characters across.

How to

How to prettify JSON in three steps

Nothing to install, nothing to configure.

Step 1

Paste the JSON into the input box, in whatever shape it is currently in.

Step 2

Press Format. It parses and re-indents immediately, on your own device.

Step 3

Copy the readable result out of the output panel.

Common failure

Why the JSON prettifier says Invalid JSON

If the tool rejects your text, the parser could not read it as JSON. It does not guess, and it does not repair. A handful of causes account for almost every rejection, and they are all things JSON simply does not allow.

Fix the offending character and paste again. The message is the same for every cause, so it is worth knowing the short list.

Trailing comma

A comma after the last item in an object or array. Legal in JavaScript, not in JSON.

Single quotes

JSON strings and keys must use double quotes. 'name' is not a JSON string.

Unquoted keys

{ name: 1 } is a JavaScript object literal. JSON needs { "name": 1 }.

Comments

Neither // nor /* */ is part of JSON, however common they are in config files.

NaN, Infinity, undefined

None of these are JSON values. Only numbers, strings, booleans, null, objects and arrays.

A wrapper around the JSON

A log prefix, a shell prompt, or a stray closing bracket copied along with the payload.

The indent

Why this JSON formatter uses two spaces

The indent here is fixed at two spaces per level. There is no dropdown, because two spaces is what the JavaScript and TypeScript world overwhelmingly uses, and it is the width most JSON you will meet already carries.

Two spaces also keeps deeply nested data inside a reasonable line width. At four spaces, a structure six levels deep starts at column twenty-four before a single character of content, which pushes long values off the side of the screen.

In code

How to pretty print JSON in JavaScript and Python

This tool is a browser front end for something your language already does. If you would rather do it in a script, both of these produce the same two-space output.

Both take a parsed value, not a string of JSON. In JavaScript that means JSON.parse first if you are starting from text; in Python it means json.loads first.

JavaScript

JSON.stringify(value, null, 2) returns the indented string. The null is the replacer argument, which you rarely need.

Python

json.dumps(data, indent=2) does the same. Add sort_keys=True if you want alphabetical keys, which this tool does not do.

Command line

Piping through a JSON-aware CLI tool will also reindent, which is handy when the payload is already in a shell pipeline.

The pair

JSON prettifier versus JSON minifier

These are opposite operations on the same data. Prettifying adds whitespace so a person can read it. Minifying strips whitespace so a machine can move it in fewer bytes. Neither changes a single value.

Use the prettifier when you are reading, debugging or committing a file. Use the minifier when you are sending the payload over a network or embedding it where size matters. You can go back and forth as many times as you like without losing anything.

Who it's for

Who uses a JSON prettifier, and when

Developers paste a minified API response in mid-debug, just to see the actual shape of what came back instead of a wall of text. People reviewing a pull request run a JSON fixture through it before committing, so the next diff on that file is readable line by line instead of showing one enormous changed line.

Support and QA staff use it on a raw payload pulled out of a bug report or a log line. And anyone handed a config file with no formatting uses it to find the one setting they came for.