JSON Formatter & Validator Online
JSON, short for JavaScript Object Notation, is the standard way that websites, apps and APIs exchange data, and sooner or later almost everyone who works with the web has to read a wall of minified JSON. This free JSON formatter and validator takes that dense, single-line text and turns it into clean, readable JSON with a two-space indent, so you can see the structure at a glance. It also validates your JSON as it formats it, which means a missing comma, an extra trailing comma or a mismatched bracket is flagged immediately instead of breaking your code later. Everything happens in your browser: your data is never uploaded to a server, stored anywhere or shared with anyone, so you can safely format configuration files and API responses on your own machine. The tool is free, needs no account and works on phones, tablets and desktop computers alike. Developers use JSON every day, from the settings file of a small website to the response of a large payment API, and readable JSON saves real time.
When an API returns an error, the first thing you usually need to know is which field is wrong, and that is much easier to find in formatted JSON than in a single line of 10,000 characters. The validator also helps beginners, because JSON has strict rules: keys must be in double quotes, there can be no trailing commas, and single quotes are not allowed. A single misplaced character makes the whole document invalid, and the error messages in this tool point you to the position of the problem so you can fix it quickly.
Formatted JSON
Enter JSON above and click Format, Minify or Validate.
What Is JSON?
JSON is a lightweight text format for storing and moving structured data. It is built from just a few pieces: objects, which are collections of key and value pairs inside curly braces; arrays, which are ordered lists inside square brackets; strings in double quotes; numbers; and the values true, false and null. A weather app, for example, might receive JSON like {"city":"Chicago","temperature":21,"conditions":"Sunny"}, and the app then reads those fields to show the forecast. The format looks simple, and it is, but it is also strict: every key must be quoted, every string must use double quotes, and commas must sit exactly between items, never after the last one.
Formatting, Minifying and Validating
Formatting, sometimes called beautifying or pretty-printing, adds line breaks and indentation so the structure of the data is visible. A two-space indent is the most common style, and it is what this tool uses. Minifying does the opposite: it removes all unnecessary whitespace so the JSON takes up as little space as possible, which is useful when you need to paste data into a URL, a small config field or a test case. Validating checks the text against the JSON rules and reports the first error it finds, including the character position where the parser stopped. Another is a missing closing brace after editing a large file by hand. This tool catches those mistakes instantly and tells you where to look.
How to Use
- Paste your JSON into the box. You can paste a minified API response, a config file or a single object. The box starts with a small valid example you can replace.
- Click Format to beautify it. The result appears below with a two-space indent, one key per line, so nested objects and arrays are easy to follow.
- Click Minify when you need compact JSON. All extra spaces and line breaks are removed, leaving a single line you can copy into a test, a URL or a config field.
- Click Validate to check the JSON without changing it. If the JSON is valid you will see a green confirmation; if not, the tool shows the error and the character position so you can fix it and try again.
Worked Example
Start with this minified JSON: {"name":"Ada","age":36}. Clicking Format produces:
{
"name": "Ada",
"age": 36
}
Clicking Minify on that formatted text returns it to the single line {"name":"Ada","age":36}. Now try something invalid, such as {"a":}. The validator reports an error like "Unexpected token } in JSON at position 5", because a key must always have a value after its colon. Fixing it to {"a":1} makes the JSON valid again. That is the whole point of the tool: the data is identical, but the readable version is far easier to check, edit and debug.
Frequently Asked Questions
Is my JSON data private when I use this formatter?
Yes. This tool runs entirely in your browser. Your JSON is never uploaded to a server, stored or shared. You can close the page and the data is gone, and nothing you paste leaves your device.
What is the difference between formatting and minifying JSON?
Formatting adds line breaks and indentation so JSON is easy for people to read, while minifying removes all unnecessary whitespace so JSON is as short as possible for machines. Both keep the data exactly the same; only the layout changes.
Why does my JSON fail validation?
The most common causes are a trailing comma after the last item, single quotes instead of double quotes, an unquoted key, or a missing closing brace or bracket. The validator shows the error and its character position, so check the text just before that position first.
Can I format very large JSON files?
Yes, for most files the tool handles tens of thousands of lines quickly because it runs locally in your browser. Extremely large files, of many megabytes, may be slower on older phones, so for those you can split the file or use a desktop browser.
Does this tool accept JSON5 or JavaScript objects?
No. This tool validates strict JSON only, which is what APIs and config files expect. That means double quotes on all keys and strings, no trailing commas, no comments and no single quotes. If your text uses those, fix them first and validate again.