JSON Formatter & Validator
Format, validate, minify, and inspect JSON with syntax error location. Choose 2-space, 4-space, or tab indentation, sort object keys alphabetically, and copy results instantly. Runs 100% in your browser without uploading data.
Why Use a Local-First JSON Formatter?
JSON is the universal data interchange format for modern APIs, microservices, and web configuration files. However, unformatted minified JSON is nearly impossible for developers to read or debug.
Many online formatters transmit your data to remote web servers, creating compliance and privacy risks when working with confidential customer data, internal tokens, or database dumps.
Castov JSON Formatter & Validator executes entirely inside your browser. No network requests are made, ensuring your proprietary payloads remain strictly private.
Syntax Validation with Precise Error Pinpointing
A single misplaced comma or unquoted key invalidates an entire JSON document. Our validator catches syntax violations and reports the exact line number, column offset, and token error message.
Use the Minify feature to strip all unnecessary whitespaces and line breaks, reducing payload size for network transmission and API benchmarking.
How to use this tool
- Paste or type your raw JSON into the input editor.
- Choose your preferred indentation (2 spaces, 4 spaces, or tab) or toggle Sort Keys.
- Click Format & Validate to prettify your JSON, or Minify to remove all unnecessary whitespace.
- Copy the formatted output to your clipboard with one click.
Examples
Standard JSON formatting, minification, and key sorting examples.
2-Space Pretty Print
{"user":"alex","roles":["admin","editor"]}
- Formatted
- { "user": "alex", "roles": [ "admin", "editor" ] }
- Indentation
- 2 spaces
Minification
{ "status": "ok", "code": 200 }
- Minified
- {"status":"ok","code":200}
- Size Reduction
- Saves ~30% whitespace bytes