JSON Formatter
FreeValidates and pretty-prints or minifies a full JSON document, with adjustable indent, optional key sorting, and exact line/column error reporting.
Runs entirely in your browser. Your JSON is never uploaded anywhere.
What this tool does
Paste a JSON document and this tool validates it, then either pretty-prints it with your chosen indentation or minifies it to a single line. Invalid JSON is reported with the exact line and column where parsing failed.
How It Works
The tool parses your input with the browser's built-in JSON parser, which builds an in-memory representation of the data (objects, arrays, strings, numbers, booleans, and null). It then serializes that representation back into text, either with line breaks and indentation inserted at every nesting level (pretty-print) or with all optional whitespace removed (minify). Optionally, object keys are sorted alphabetically before serializing, recursively at every level, without touching array order.
Problems it solves
- Making a minified API response or config file readable for debugging.
- Finding exactly where a JSON document is malformed, down to the line and column.
- Shrinking a JSON file before sending it, by removing unnecessary whitespace.
- Normalizing key order across JSON documents to make them easier to compare.
Frequently asked questions
›What is the difference between this and the JSON Encoder tool?
This tool takes a full JSON document (an object or array) and validates, pretty-prints, or minifies its structure. The JSON Encoder tool instead converts a single plain-text string into (or out of) a JSON string literal. They solve different problems.
›Why does it tell me my JSON has an error at a specific line and column?
The browser's JSON parser reports the character position where it got stuck, and this tool converts that position into a line and column number by counting line breaks, so you can jump straight to the problem instead of scanning the whole document.
›What does sorting keys alphabetically do?
It recursively reorders the keys of every object in the document into alphabetical order, while leaving array order untouched (since array order is meaningful and reordering it would change the data). This makes it easier to diff two JSON documents or find a specific key by eye.
›Does formatting or minifying change the data itself?
No. Both operations only change whitespace between the JSON tokens. The values, keys, and their order (except when you explicitly enable key sorting) remain exactly the same.
›Can this handle very large JSON files?
Since everything runs in your browser using its native JSON parser, the practical limit is your device's available memory rather than any limit imposed by this tool, though extremely large documents (tens of megabytes) may feel slow in a textarea.
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