JSON Formatter & Validator
Format, minify, and validate JSON payloads locally in your browser with line and column syntax diagnostics.
About the JSON Formatter & Validator
The API Toolkit JSON Formatter & Validator helps developers inspect, beautify, minify, and validate raw JSON strings directly in the browser. It adheres strictly to the RFC 8259 specification and pinpoints syntax errors with 1-based line and column diagnostics.
How It Works
- Format: Pretty-prints valid JSON with 2 spaces, 4 spaces, or tab indentation.
- Minify: Strips whitespace and newlines to compact payloads for HTTP transport or configuration strings.
- Validate: Checks syntax compliance and highlights trailing commas, unquoted keys, or missing brackets with line and column numbers.
Privacy & Constraints
- 100% Local Processing: Uses native browser
JSON.parse()andJSON.stringify(). Your data is never uploaded to any server. - 5 MB Safety Cap: Payloads up to 5 MB are supported to keep your browser tab fast and responsive.
- Strict RFC 8259: Comments, trailing commas, and single-quoted strings are flagged as syntax errors.
Frequently Asked Questions
Is my JSON data safe when using this formatter?
Yes. Every action in this tool executes locally inside your browser tab. No network requests are sent when you paste, format, minify, or validate JSON, making it safe for inspecting payloads containing internal schemas or staging data. See our Privacy Policy.
Why does my JSON fail validation because of a trailing comma?
While JavaScript objects allow trailing commas, the official JSON standard (RFC 8259) strictly forbids a comma after the last element in an array or the last property in an object. Remove the trailing comma to make the payload valid across all parsers.
Can this formatter handle JSON arrays or primitive root values?
Yes. In accordance with RFC 8259, a valid JSON document can have an object ({}), an array ([]), or a standalone string, number, boolean (true/false), or null at the root level.
Does formatting JSON execute any embedded scripts?
Never. Input is parsed strictly as data via JSON.parse() and placed into a read-only text editor. We never use eval() or inject raw HTML into the DOM.