Completely FREE JSON formatter and validator. No signup, no upload. Paste JSON and instantly get it validated and re-formatted: pretty-printed with your choice of indentation, minified to a single line, or with object keys sorted alphabetically. Invalid JSON gets a clear error with the line and column of the first problem. API responses, config files, and payloads never leave your browser.
Your data never reaches us
Nifty Utilities has no backend server, database, user accounts, or endpoint capable of receiving your tool inputs. Files and entries are processed inside your browser. We cannot view, capture, or store them.
Validate first, format second
The tool parses your input with the browser's native JSON parser — the same strict parser your code will use. If parsing succeeds you get a green checkmark plus structure statistics: how many objects, arrays, strings, and numbers, and how deeply nested the data goes. If parsing fails, the error message is shown along with the line, column, and a snippet of the text surrounding the problem, so you can jump straight to the offending character instead of scanning the whole payload.
The errors that cause most invalid JSON
A few mistakes account for nearly all validation failures. Trailing commas — legal in JavaScript, illegal in JSON — after the last item of an object or array. Single quotes instead of double quotes around strings and keys. Unquoted keys, again a JavaScript habit. Comments, which JSON does not allow at all. And stray control characters from copying out of terminals or logs. When the error message says "Unexpected token", the snippet this tool shows you almost always contains one of these.
Pretty vs. minified
Pretty-printed JSON with 2-space or 4-space indentation is for humans: code reviews, documentation, debugging a fat API response. Minified JSON — everything on one line, no whitespace — is for machines and transfer size; it's the format you paste into an environment variable or ship in a request body. The two are byte-for-byte equivalent to a parser, so convert freely in both directions.
Sorting keys
Enabling sort keys rewrites every object with its keys in alphabetical order, recursively. JSON key order carries no meaning to a parser, but sorted keys make two payloads comparable: sort both, then diff them, and structural differences surface immediately instead of hiding behind ordering noise. It also makes long config files easier to scan.
Privacy note for API data
JSON payloads routinely contain tokens, emails, and account data — exactly the things not to paste into a random web form. This formatter runs entirely in your browser. There is no server component, no logging, and nothing survives closing the tab.
Frequently asked questions
Does this tool fix invalid JSON automatically?
No — it tells you precisely where the first error is so you can fix it. Automatic "repair" tools have to guess what you meant, and a wrong guess in a config file or payload is worse than an error message. The line, column, and context snippet make manual fixes fast.
What's the difference between JSON and a JavaScript object?
JSON is stricter: keys must be double-quoted strings, strings must use double quotes, and there are no comments, trailing commas, undefined, or functions. Valid JSON is valid JavaScript, but much valid JavaScript is invalid JSON — which is why code pasted from a JS file often fails validation.
Can it handle large files?
It comfortably handles payloads up to several megabytes — typical API responses and config files parse instantly. Extremely large files (tens of megabytes) may be slow to render in the output box even though parsing succeeds.
Important
This tool provides estimates and general-purpose documents, not financial, tax, legal, or professional advice. Verify important results before relying on them.
Support
Problem with this tool or suggestions for improvement? Please email support@niftyutilities.com.