JSON Formatter
Format, validate, and minify JSON instantly in your browser.
'Format' to pretty-print, 'Minify' to one line. All processing happens only in your browser.
What formatting and minifying actually do
Under the hood, this tool parses your text into a real JSON value and then serializes it again. Formatting (pretty-printing) re-emits that value with line breaks and 2-space indentation so nesting is visible, while minifying re-emits the same value with every non-essential space and newline removed so it fits on one line. Because both start by parsing, the round trip also acts as a validation pass: if the text is not valid JSON, it cannot be parsed and you get an error instead of output. Crucially, only whitespace changes. Key order, values, numbers, and strings are preserved exactly, so formatting a payload and then minifying it gives you back byte-for-byte equivalent data.
A concrete example
Suppose an API returns this on one line: {"user":{"id":42,"roles":["admin","editor"],"active":true},"lastLogin":null}. Pasted as-is, it is hard to see where the user object ends or how many roles exist. After formatting, each key sits on its own indented line, the roles array is stacked vertically, and the shape of the object is obvious at a glance. If you accidentally left a trailing comma after "editor" or forgot the closing brace, the parser stops and points you near the offending character rather than silently guessing. Minifying the formatted version collapses it straight back to the compact single line, which is what you would store in a config value or send over the wire.
When and why to reach for it
- Debugging API responses: paste a compact response from your browser network tab or a curl command, format it, and read the structure top to bottom instead of scanning a wall of text.
- Cleaning up hand-edited config: after manually editing a settings or package file, run it through to confirm you did not break a bracket or quote before committing it.
- Preparing data to embed: minify a JSON blob before pasting it into a source-code string, an environment variable, or a URL parameter where line breaks would cause problems.
- Comparing two payloads: format both so they use identical indentation, which makes a line-by-line diff meaningful instead of noisy.
Common mistakes and misconceptions
- Confusing JSON with a JavaScript object literal. JSON requires double quotes around every key and string, forbids single quotes, and does not allow unquoted keys, so a snippet copied straight from JS code often fails.
- Leaving a trailing comma after the last item in an object or array. It is legal in modern JavaScript but invalid in JSON, and it is one of the most frequent parse errors.
- Expecting comments to survive. JSON has no comment syntax, so // and /* */ are treated as errors even though many config tools tolerate them.
- Assuming formatting fixes data. It only changes layout. A wrong value, a misspelled key, or a duplicate key is not corrected, and duplicate keys may silently collapse to the last one during parsing.
- Pasting a value wrapped in extra quotes. A JSON string that itself contains escaped JSON is still just a string until you unescape it, so it will format as one long quoted line rather than a nested object.
Limits and cautions
This tool follows the strict JSON standard, so it will not accept relaxed variants such as JSON5, comments, or single-quoted strings without cleanup first. Extremely large inputs are held entirely in memory and re-rendered in the page, so a file of several megabytes can make the browser feel slow or unresponsive, and in that case a desktop editor or a streaming parser is a better fit. Numbers are parsed with standard floating-point rules, which means values beyond the safe integer range or with very high precision may be represented approximately rather than exactly. When precision matters, keep such values as strings.
Privacy: everything stays in your browser
All parsing, formatting, validation, and minifying run locally using the browser's built-in JSON engine. Your text is never uploaded, logged, or stored on any server, and nothing leaves the page. That makes it safe to paste responses that contain tokens, personal data, or internal identifiers. If you want to be completely certain, you can disconnect from the network and the tool will still work, because there is no server call involved at any step.
The JSON you enter is processed only in your browser and is never sent to or stored on a server. You can safely paste JSON with sensitive data.
Read the Privacy Policy →Frequently asked questions
Why does my JSON fail even though it looks correct?
The most common causes are a trailing comma after the last element, single quotes instead of double quotes, unquoted keys, or a value copied from JavaScript rather than true JSON. The error message points near the character where parsing stopped, so start reading a little before that spot. Remove comments and trailing commas, and make sure every key and string uses double quotes.
Is my data sent to a server?
No. Formatting, validation, and minifying all run in your browser using its standard JSON parser, and your input is never sent to or stored on a server. This means even sensitive payloads such as access tokens or personal data stay entirely on your device.
What is the difference between formatting and minifying?
Formatting adds indentation and line breaks so the structure is easy to read, while minifying strips all optional whitespace so the JSON occupies a single compact line. Both preserve the exact same data and values, so you can move back and forth freely without changing meaning. Use formatting to inspect and debug, and minifying to store or transmit.
Does it accept JSON with comments or trailing commas?
No, because the strict JSON standard allows neither. Comments (// and /* */) and a comma after the final item in an object or array are treated as syntax errors. Remove them first, or use a tool designed for relaxed variants like JSON5 if you need those features.
Will formatting change or reorder my data?
No. Only whitespace and layout change; key order, values, arrays, and nesting are all preserved. One caveat is that if your input contains duplicate keys in the same object, the parser keeps only one of them, so the output may drop a duplicate. Otherwise the data is identical to what you pasted in.
Can it handle very large JSON files?
It can, but everything is held in memory and re-rendered in the page, so files of several megabytes may make the browser slow or briefly unresponsive. For occasional large inputs it usually still works if you give it a moment. For routine work with huge files, a desktop editor or a command-line streaming tool is a better choice.