Free JSON validator and formatter — validate JSON syntax with error highlighting. Free online JSON validation tool.
Validate and format JSON data with error highlighting. Pretty print and minify options. Works 100% in your browser.
JSON Input
Copied!
!
Output
Validated JSON will appear here
Disclaimer: This tool processes all data locally in your browser. No JSON data is sent to any server. Validation is performed using native JavaScript JSON.parse().
What the JSON Validator & Formatter Does and Why It Matters
This tool checks whether JSON is syntactically valid and, when it is, formats it with clean indentation and syntax highlighting. When it is not, it points to the position of the error so you can fix it quickly.
JSON drives APIs, config files, and data exchange, and a single misplaced comma or quote breaks the whole document. Validating and pretty-printing in the browser turns a frustrating hunt into a quick, visual fix.
How to Use JSON Validator & Formatter
Paste your JSON into the input area.
Run validation to check the syntax.
If there is an error, read the position indicator and correct it.
Once valid, review the formatted, highlighted output.
Copy the clean JSON for your file or request.
Re-validate after edits to confirm it is well-formed.
Supported Inputs and Limitations
Supported input
Any JSON text, valid or invalid
Minified or pretty-printed JSON
What you get
A valid / invalid verdict
The error location when parsing fails
Formatted, syntax-highlighted JSON when valid
Known limitations
It checks JSON syntax, not whether the data matches a particular schema.
It validates structure, not the correctness or meaning of the values.
Extremely large documents may be slower to render in the browser.
Privacy and Security
Validation and formatting happen locally in your browser, so the JSON you paste is never uploaded to NovaTools and nothing is stored. You can safely check payloads that contain internal data.
Frequently Asked Questions
What does the error position tell me?
It points to where the parser stopped — usually right at or just before the problem, such as a missing comma, an unquoted key, or a trailing comma. Fixing that spot typically resolves the error.
Does this validate against a schema?
No. It checks that the JSON is syntactically well-formed. Validating against a specific JSON Schema (required fields, types, etc.) is a separate kind of check.
Is my JSON sent anywhere?
No. Parsing and formatting run entirely in your browser, so payloads with internal or sensitive data stay on your device.
JSON (JavaScript Object Notation) is the de facto standard for data exchange on the web. This free online tool helps you validate JSON syntax and format it for readability. Whether you're debugging API responses, preparing configuration files, or cleaning up data, this validator provides instant feedback with precise error positioning and syntax highlighting.
How to Use
Paste your JSON into the input area.
Click Pretty Print to format with indentation and syntax highlighting.
Click Minify to compress JSON for transmission or storage.
If your JSON has errors, the tool will highlight the exact position and describe the issue.
Use Copy or Download to save your formatted JSON.
Frequently Asked Questions
How does the error position indicator work?
When your JSON contains syntax errors, the validator uses JavaScript's native error parsing to extract the exact character position where the error occurred. This helps you quickly locate and fix issues in large JSON files.
Is my JSON data kept private?
Absolutely. All validation and formatting happens entirely in your browser using JavaScript. No data is ever transmitted to any server, logged, or stored. You can safely use this tool with sensitive API responses or configuration files.
What's the difference between Pretty Print and Minify?
Pretty Print adds line breaks and indentation to make JSON human-readable, ideal for debugging and editing. Minify removes all whitespace to produce the smallest possible JSON string, perfect for network transmission or storage optimization.
What do the syntax highlight colors mean?
Keys are shown in cyan, string values in green, numbers in orange, booleans (true/false) in purple, and null values in red. These colors follow popular code editor conventions for quick visual parsing.
Does this tool support large JSON files?
Yes, the tool can handle JSON files of significant size, limited only by your browser's memory. However, extremely large files (tens of megabytes) may cause performance issues depending on your device.
Recommended next reading
Use these practical guides to understand when this tool is the right choice, what to check before exporting, and which workflow usually comes next.
