JSON Formatter & Validator
Format, minify, and validate JSON instantly. Detect errors, adjust indentation. Free, private, browser-based.
How to Use
- 1. Paste your JSON into the input box.
- 2. Choose Format (pretty-print) or Minify.
- 3. Select your preferred indentation (2 spaces, 4 spaces, or tab).
- 4. Click the button. Copy the result or fix any errors shown.
About This Tool
JSON (JavaScript Object Notation) is the most widely used data interchange format in modern software development. It is used for APIs, configuration files, databases, and virtually every web application. Despite its ubiquity, JSON can be hard to read when unformatted — especially when returned from APIs as a single minified line.
This tool provides two core functions: formatting (also called pretty-printing or beautifying) adds indentation and line breaks to make the JSON structure visually clear; minifying removes all unnecessary whitespace to minimize file size for production use or transmission.
The tool also validates your JSON as part of formatting. If your JSON contains syntax errors — such as trailing commas (which are not valid in JSON), single quotes instead of double quotes, unquoted keys, or missing brackets — the error message will tell you exactly what went wrong so you can fix it.
All processing uses the browser's native JSON.parse() and JSON.stringify() functions, which are the gold standard for JSON handling in JavaScript environments. Your data never leaves your browser. This tool works offline once the page is loaded.
You may also find our JSON Diff, JSON to CSV, and YAML to JSON helpful.
Looking for a free JSONFormatter.org alternative? See how UseToolify compares.
Frequently Asked Questions
What does JSON formatting do?
JSON formatting (also called "pretty-printing") adds indentation and line breaks to make compact or unreadable JSON easy to read and understand.
What does JSON minification do?
Minification removes all whitespace (spaces, tabs, newlines) from JSON, making it as compact as possible. This reduces file size for transmission over networks.
What happens if my JSON is invalid?
The tool displays a clear error message showing what went wrong. Common issues include trailing commas (not valid in JSON), single quotes instead of double quotes, and unquoted keys.
Can I format very large JSON files?
Yes, but very large JSON (over 10MB) may slow down the browser. For large files, consider using a command-line tool like jq or a code editor with JSON formatting built in.
Does this tool send my JSON anywhere?
No. All formatting and validation happens in your browser using the native JSON.parse() and JSON.stringify() functions. Your data never leaves your device.
Is it safe to paste API keys, tokens, or passwords into an online JSON formatter?
With this tool, yes — nothing is uploaded, so there is nothing to leak. That said, some online formatters have been caught storing pasted data on their servers, and a few expose "save" or "share" links that are public and guessable by anyone. This tool has no save, share, or upload feature at all: your JSON is parsed in memory by your browser and is gone the moment you close or refresh the tab.
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Guide
How to format, minify and validate JSON in your browser
Paste JSON into the box and the tool does one of two things. Format rewrites it with line breaks and indentation so a human can read it. Minify strips all optional whitespace so it takes the fewest characters. Both begin by parsing your input with the browser's own JSON.parse, so success also tells you the input was valid, and failure shows the parser's error message.
It suits developers reading an API response that arrived as one long line, people editing a sample payload or config file, and anyone handed a JSON export to understand. It is deliberately simple: no tree view, no key sorting and no automatic repair. Knowing what the parser accepts, and where re-printing changes your data, saves debugging time.
Step by step
- Paste your JSON into the Input box. The placeholder shows a tiny example, {"key": "value", "number": 42}.
- Pick a mode with the Format and Minify buttons above the box. Format is selected when the page opens.
- In Format mode an Indent drop-down appears with 2 spaces, 4 spaces and 1 tab.
- Click the wide yellow button, labelled Format JSON or Minify JSON. Nothing runs until you click, and changing the mode or indent afterwards needs another click.
- On success the result appears in the Output box. Press Copy and the label changes to Copied!.
- On failure a red message shows the parser's error and earlier output is cleared. Fix the input and click again.
When this is useful
- Reading a minified API response copied from browser developer tools.
- Checking that a hand-edited configuration file is still valid JSON before you save it.
- Shrinking a payload to one line so it can sit inside a request body field or an environment variable.
- Learning how nested objects and arrays fit together by looking at an indented sample, such as an invoice.
- Working out why an API call rejects your body, using the error position as a clue.
Worked example: Reading a compact invoice payload
You paste this 173-character line: {"invoice":"INV-2041","customer":{"name":"Ravi Traders","gstin":"29ABCDE1234F1Z5"},"items":[{"sku":"A1","qty":2,"rate":450.5},{"sku":"B7","qty":1,"rate":1299}],"paid":false}. Format with 2 spaces turns it into 20 lines and 276 characters, and 4 spaces gives 348 characters. Minify returns the original 173. Now add a stray comma before the final brace, so the end reads "paid":false,}. In a Chromium-based browser the tool shows: Expected double-quoted property name in JSON at position 173 (line 1 column 174). Delete the comma and the output returns.
Tips for better results
- Read the position in the error message. Chromium-based browsers report character position with line and column, while Firefox and Safari word errors differently, because the message comes from the browser.
- The parser reports where it noticed the problem, which can be after the real mistake. For unbalanced brackets, look earlier in the text.
- JSON is strict: double quotes only, no trailing commas, no comments, and no NaN or undefined. Convert JavaScript object literals before pasting.
- A lone string or number is valid JSON too, so a quoted word or the digit 5 formats without complaint.
Common mistakes
- Pasting a JavaScript object or Python dictionary. Single quotes, unquoted keys, True, False and None all fail. Use double quotes, quote the keys and write true, false and null.
- Leaving a trailing comma or a comment. Some config formats allow them, but strict JSON does not, and the error will point near the comma.
- Trusting very large numbers. Values are parsed as JavaScript numbers, so integers beyond 9,007,199,254,740,991 lose digits: 12345678901234567890 comes back as 12345678901234567000. Keep such identifiers as strings. Also 1.0 is printed as 1.
- Assuming the output preserves everything. If an object repeats a key only the last value survives, and keys that look like whole numbers move to the front in ascending order, so {"b":1,"2":"x","a":2,"1":"y"} becomes {"1":"y","2":"x","b":1,"a":2}.
- Pasting formatted output into a place that converts tabs to spaces. If your editor or form changes tab characters, pick 2 or 4 spaces instead.
Your files and privacy
Parsing and printing happen in your browser with JSON.parse and JSON.stringify. The tool's code makes no network request with your input and does not store or log it, and reloading the page clears the boxes. As a habit, remove real tokens, passwords and personal data from a payload before sharing the formatted result elsewhere.
Frequently asked questions
What is the difference between valid JSON and a JavaScript object?
JSON is a text format with stricter rules: keys and strings need double quotes, trailing commas and comments are not allowed, and values are limited to objects, arrays, strings, numbers, true, false and null. Code that looks fine in JavaScript can still fail here.
Does formatting change my data?
The structure and values stay the same, but the text is re-printed. Numbers are normalised (1.0 becomes 1 and 1e3 becomes 1000), escaped characters such as \u0939 appear as the actual character, and duplicate keys collapse to the last one.
Can it repair broken JSON automatically?
No. It reports the first error the parser meets, then you fix the input and run it again. It will not guess at missing quotes or commas, and it cannot sort keys or show a collapsible tree.
Is there a size limit?
The tool sets none, but everything runs in your browser tab. A document of tens of megabytes can make the tab slow or unresponsive, and a command-line tool such as jq handles such files better.
Why does the error message look different in another browser?
The message is produced by the browser's own JSON parser, not by this site. Chrome, Firefox and Safari word and position their errors differently, although they agree on whether the input is valid.
Guide reviewed 2026-10-11 by the useToolify team.
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