Home › Text tools › JSON Formatter & Validator

JSON Formatter & Validator

Minified JSON from an API is impossible to read, while a missing comma makes it invalid. This free JSON formatter and validator pretty-prints your JSON with clean indentation, minifies it for compact storage, and tells you exactly where a parse error is — all privately in your browser.

Mode

JSON input

Formatted JSON

Paste JSON to format.

What is a JSON Formatter & Validator?

A JSON formatter takes a blob of JSON (JavaScript Object Notation) and reformats it so it is easy to read, typically by adding indentation and line breaks. A companion function minifies it, removing all optional whitespace so the data is as small as possible for storage or transmission.

Because JSON is the exchange format of the web, nearly every API, config file and database works with it. Tools that output JSON rarely make it human-readable, and hand-written JSON is prone to errors. The validator parses your input and reports the exact location of any problem, so you can fix a misplaced comma, a missing quote or a trailing comma quickly.

Developers, data analysts and site owners use it to debug an API response, to tidy a config file such as package.json, to review a data export, and to prepare compact JSON for a web request. Formatting and validating locally means your data, including anything confidential, never leaves your machine.

How to use the JSON Formatter & Validator

Paste your JSON into the input area.
Choose a mode: Format (pretty-print) or Minify.
Click Format to run it.
Read the output in the result area, with the status message confirming the JSON is valid or pointing to the error.
Copy the result or Clear to start over.

Example

Input: {"name":"toolcubby","tags":["seo","tools"]}

Format (2 spaces) →

{ "name": "toolcubby", "tags": [ "seo", "tools" ] }

The status confirms “Valid JSON ✓”.

Who is this JSON Formatter for?

JSON is the language of APIs, config files and the web, so the people who reach for a formatter and validator come from every side of a project.

Developers: debug API responses and tidy JSON config files such as package.json without leaving the browser.
Writers and content creators: cleaning up code snippets and JSON samples they paste into blog posts and documentation.
Marketers: checking tracking payloads and structured data markup so nothing malformed breaks a campaign.
Analysts: reviewing exported JSON from databases or report tools before loading it into a spreadsheet or pipeline.

JSON reference: common syntax errors

A quick reference to the errors this validator catches most often, so you can spot and fix them faster.

Issue	Invalid example	Why it fails
Trailing comma	{"name":"a",}	Valid only for empty objects/arrays in JS; JSON forbids a trailing comma after last item.
Single quotes	{'name':'a'}	Keys and string values must use double quotes in JSON.
Missing comma	{"name":"a" "age":3}	A value must be followed by a comma before the next key.
Unquoted key	{name:"a"}	Every key must be a double-quoted string.
Lowercase boolean	{"ok":true}	true, false and null are lowercase. This is valid JSON.
Unescaped inner quote	{"a":"say "hi""}	Inner quotes must be escaped as \" inside a JSON string.

Common use cases

Reading a minified API response to debug or document it.
Tidying a package.json or other JSON config file for editing.
Preparing compact JSON to send in a web request or store in a database.
Catching syntax errors in hand-written JSON before it breaks an app.

Pro tips

Use the status message to validate first — a valid JSON output means the input parsed correctly.
Minify reduces size for storage and transfer, so provide minified output when shipping data to a backend.
For very large files, paste in sections; a single malformed ending can make the whole parse fail.
Remember booleans and null must be lowercase (true, false, null) and keys must be in double quotes for the JSON to be valid.

FAQ

What is JSON formatting?

It is the process of adding indentation, line breaks and spacing to a JSON string so it is readable, while keeping the data identical.

What does minify do?

Minify removes all unnecessary whitespace from JSON to make it as small as possible, which is useful for storage and faster transmission.

What is the difference between format and validate?

Formatting reorganises the output for readability; validation checks that the input is correct JSON and reports any syntax error.

Why is my JSON invalid?

Common causes are a trailing comma, keys or strings not wrapped in double quotes, missing commas between entries, or using single quotes where double quotes are required.

Does it upload my JSON anywhere?

No. Formatting and validation run entirely in your browser, so your data never leaves your device.

What indentation does pretty-print use?

It uses two spaces by default, which is the most widely used convention, producing clean, readable nested output.

Can it handle very large JSON?

Yes, both formatting and minification handle large inputs quickly, though very big files are easiest to work with in sections.

Is it free?

Yes, free and unlimited with no signup required.