JSON Beautifier — format and pretty-print JSON online

Paste minified or badly indented JSON and get it back readable, with the indentation you prefer. The data is untouched — only whitespace changes. Everything runs in your browser, so nothing is uploaded.

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Beautified JSON

Beautifier or validator — which one do you want?

Both pages pretty-print valid JSON, so the honest answer is that they overlap. The difference is what you are trying to find out.

	This page	JSON validator
The question it answers	Make this readable, my way	Is this broken, and where?
Your input	Kept — output appears beside it	Replaced in place by the result
Indentation	2 spaces, 4 spaces or a tab	Always 2 spaces
Broken JSON	Reports the line and column	Reports it and can repair it
Result	Copy or download it	Copy it, or share a link
Very large files	Results over 20 MB download	Preview and summary up to 50 MB

In short: come here when the JSON already works and you want it laid out a particular way. Go to the validator when something is wrong and you need to know what.

What beautifying actually changes

Nothing that matters. JSON treats whitespace between tokens as insignificant, so {"a":1} and a version of it spread over four indented lines are the same document to every parser. Beautifying re-emits the same values with newlines and indentation added; it does not change a number, a string, or the order of an array.

This matters when you are debugging: a 4,000-character single-line API response and its formatted equivalent are byte-for-byte different and semantically identical. If you need to know whether two documents actually differ, format is the wrong lens — use the JSON diff, which compares the data rather than the text.

Two spaces, four spaces, or tabs

There is no correct answer and no standard — JSON says nothing about indentation. Two spaces is what JSON.stringify(value, null, 2) produces and what most JavaScript tooling emits, so it is the default here. Four spaces is common in Python codebases, where json.dumps(obj, indent=4) is the usual incantation. Tabs are the smallest on disk and let each reader choose their own width.

Pick whichever matches the file's neighbours. Reformatting a checked-in file with different indentation rewrites every line in the diff, which is a real cost at review time for no benefit.

One thing that is not preserved: numeric-looking keys

Formatting works by parsing the document and re-serialising it, so object keys come back in the order JavaScript holds them — and JavaScript puts integer-like keys first, in ascending numeric order, ahead of every other key. {"10":"a","2":"b","name":"c"} formats to 2, then 10, then name.

This is a property of the language, not of this tool, and it is harmless: JSON objects are unordered by definition, so no conforming consumer can depend on key order. It is worth knowing before you wonder why the output moved. Ordinary string keys keep their original order.

If it will not format, it will not parse

A beautifier has to parse before it can print, so invalid JSON produces an error rather than formatted output. The error above reports the exact line and column. For a document you cannot immediately fix, the JSON validator can repair the common mistakes — trailing commas, single quotes, unquoted keys — and the JSON error reference explains what each parser message means.

Large files

Parsing and re-serialising run in a Web Worker, off the main thread, so the page stays responsive while it works. Up to 20 MB the result is loaded into the editor on the right; past that it is offered as a download instead, because holding two documents that size in one tab is what actually costs memory. The hard ceiling is 50 MB — measured, not guessed.

Nothing is uploaded

Your JSON is parsed by your own browser. There is no server round-trip, no account, and no size limit imposed by someone else's upload form — which means credentials, customer records and internal API responses can be formatted here without being sent anywhere.