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JSON Formatter & Validator

Format and validate JSON instantly online. Free JSON pretty-printer with syntax error detection and 2-space indentation. No signup required.

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JSON (JavaScript Object Notation) was formalized in RFC 8259 and is the dominant data interchange format for web APIs, configuration files, and databases. Raw JSON returned by APIs or stored in logs is often minified — no whitespace, all on one line — making it unreadable for debugging or code review without a formatter.

JSON formatting is essential in everyday development workflows: pretty-printing API responses in Postman or curl output, reading configuration files for AWS IAM policies or GitHub Actions workflows, auditing Elasticsearch mappings, and understanding nested MongoDB documents. Minification matters equally for production — every byte counts in high-traffic API responses.

This tool formats JSON using JavaScript's built-in JSON.parse() and JSON.stringify() with 2-space indentation, with a minify mode that strips all non-significant whitespace. A 'Try to Fix' feature uses the jsonrepair library to automatically correct common JSON errors — missing quotes, trailing commas, JavaScript-style comments — before parsing.

Common Use Cases

Debugging REST API responses

When curl or a network tab returns a minified JSON blob from a REST API like Stripe, GitHub, or Salesforce, developers paste it into a formatter to navigate the structure. Pretty-printing reveals nested objects, array lengths, and field names that are invisible in a single-line representation, reducing debugging time significantly.

Auditing AWS IAM policy documents

AWS IAM policies are stored and returned as compact JSON strings. When reviewing permissions for security audits — checking for overly broad s3:* actions or missing condition blocks — the formatted view makes the policy's Allow/Deny structure, resource ARN patterns, and condition operators easy to read and compare.

Minimizing JSON for production payloads

Mobile apps and high-throughput APIs benefit from minified JSON in bundled configuration files, feature flag definitions, or i18n translation files shipped to clients. Removing all whitespace from a 50KB translation file can reduce its size by 15–20%, improving load time on slow connections without changing any semantic content.

Repairing malformed JSON from logs

Application logs, browser console output, and copy-pasted code snippets often contain near-JSON with trailing commas after the last array element, unquoted keys, or JavaScript-style // comments. The jsonrepair integration fixes these automatically, allowing developers to parse log fragments that would otherwise require manual character-by-character correction.

How to Use the JSON Formatter

  1. Paste your raw or minified JSON in the left panel.
  2. The formatted output with 2-space indentation appears on the right.
  3. Syntax errors are shown instantly with a descriptive message.
  4. Click "Copy Output" to copy the formatted JSON.
  5. Use "Download" to save the result as a .json file.

Features