JSON Formatter & Validator Online
A powerful JSON beautifier and syntax checker. Format, structure, minify, and validate complex JSON payloads instantly in your browser.
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What Is JSON?
JSON (JavaScript Object Notation) is an incredibly lightweight, text-based data interchange format. While originally derived from the JavaScript programming language, it is entirely language-independent. Over the last decade, JSON has fundamentally replaced XML as the standard methodology for sending data back and forth between web servers and client applications (APIs).
Because JSON primarily consists of basic key-value pairs (`"name": "John"`) or arrays (`[1, 2, 3]`), it is easy for humans to read and write, and extremely easy for machines to parse and algorithmically generate.
How to Validate JSON Online
A single misplaced character will break a JSON payload, resulting in dreaded HTTP 400 Bad Request API errors or crashing your frontend interface. Using a JSON syntax checker manually verifies standard compliance before deployment.
To use our validator:
- Copy the unformatted JSON data.
- Paste the snippet directly into the large code editor block above.
- The built-in error engine will instantly analyze the structural integrity. If there is a break in syntax rules, the exact line and position of the unexpected token will be flagged in bright red.
- Make the required corrections and click Prettify JSON to reformat the document cleanly.
Common JSON Errors
When working heavily in configurations or deeply nested APIs, these repetitive syntax mistakes often trigger "JSON error unexpected token" warnings. Keep an eye out for these strict structural requirements:
- Missing Comma: Items in an array or object properties must be separated by commas. Failing to place a comma between siblings is the most frequent formatting mistake.
- Trailing Comma: Unlike modern Javascript or Python dicts, standard compliant JSON completely forbids a comma after the last property of an object or array (e.g., `{"key": "value",}`).
- Incorrect Quotes: In strict JSON, string properties and object keys must ALWAYS be enclosed within double quotes (`"`). Single quotes (`'`) or unquoted keys will critically fail to parse.
- Missing Bracket or Brace: Forgetting to close an array bracket `]` or an object brace `}` will corrupt the hierarchical nesting structure.
JSON Formatter vs JSON Minifier
JSON Formatter (Pretty Print)
JSON formatting—or "beautifying"—solves the problem of legibility. API responses often arrive back as a dense, single-line string that is impossible for a human developer to comfortably scan. Clicking "Prettify" injects whitespace spacing, tabs, and new lines to clearly outline parental and sibling object hierarchy. You can use 2 spaces, 4 spaces, or tab string formatting based on your team's code formatting rules.
JSON Minifier
Minification is the direct inverse of formatting. It aggressively strips away ALL spaces, tabs, newline indicators (`\n`), and comments. The goal is strictly size reduction.
A highly nested, formatted 500KB JSON payload might only be 350KB when correctly minified. Prior to executing long-polling network requests or storing data configurations in limited local storage spaces, developers should routinely minify the payload structure back down.
Frequently Asked Questions
How to format JSON?
Simply paste your unformatted JSON block into the editor and click the 'Prettify' button. Our tool automatically aligns brackets and indents data cleanly using 2 or 4 spaces.
How to validate JSON?
As soon as you paste JSON into our tool, it runs an instant real-time validation check using strict JSON.parse logic. Any errors will be highlighted in red with exactly which line and column the syntax break occurred.
What is JSON lint?
JSON lint (or linting) is the process of checking your JSON code for programmatic and stylistic errors. A JSON linter points out illegal characters, missing commas, unescaped strings, and structural flaws.
How to fix JSON errors?
Check the line number our validator highlights. Common errors include missing quotes around keys, trailing commas at the end of an array or object, or using single quotes instead of double quotes. Fix the character, and the error badge will turn green.
Is this JSON formatter free?
Yes, our JSON formatter and validator is 100% free with unlimited usages. There are no size restrictions up to typical browser memory limitations.
Does this tool store my data?
No. All formatting, minifying, and validation happen securely on the client-side within your browser. Your sensitive JSON payloads are never transmitted to or stored on any server.
What is JSON pretty print?
JSON pretty print is just another term for JSON formatting. It takes minified, bundled JSON data and adds line breaks and structural indentation (like spaces or tabs) to make it easily readable for humans.
Can I minify JSON online?
Yes! Clicking the 'Minify' button will instantly compress your JSON by stripping all unnecessary whitespace and carriage returns, generating a single-line compact payload ready for network requests.