JSON Formatter & Validator: Format, Validate and Minify JSON Online
Every developer works with JSON daily — API responses, configuration files, data exports, and more. A good JSON formatter is one of those tools you use dozens of times per day without thinking about it. Formly's JSON formatter formats, validates, and minifies JSON instantly with detailed error messages.
Try JSON Formatter Free →What JSON Formatting Does
Raw JSON from APIs often arrives as an unreadable single line. Formatting adds indentation and line breaks to make the structure visible. Minification does the opposite — removes all whitespace to reduce file size for transmission. Formly supports both with configurable indentation (2 spaces, 4 spaces, or tab).
JSON Validation: What It Checks
Valid JSON must follow strict syntax: strings are double-quoted (not single), trailing commas are not allowed, keys must be strings, and the document must have exactly one root element. Common errors include: missing commas between array elements, extra commas after the last element, unquoted keys, and unescaped special characters in strings.
JSON Formatter vs JSON Editor
A formatter is for read-only formatting — you paste JSON and get formatted output. A JSON editor lets you navigate and modify the JSON tree interactively. Formly offers both modes: paste-and-format for quick checks, and interactive tree view for exploring complex nested structures.
Sponsored
Common JSON Errors Explained
"Unexpected token" — usually a missing comma, extra comma, or unquoted string. "Expected property name" — key not in quotes. "Unterminated string" — a string value is missing its closing quote. The formatter shows the exact line and character position of errors.
Working with Large JSON Files
For JSON files over 1MB, loading in the browser can be slow. The formatter handles up to 10MB efficiently. For larger files, use jq (command line) or a dedicated JSON editor. For API development, tools like Postman have built-in JSON formatting.
JSON Schema Validation
Beyond syntax validation, JSON Schema validates that JSON data matches a defined structure. For example, ensuring all required fields are present, values are the correct type, and string fields match specific patterns. This is essential for API development — Formly supports JSON Schema validation alongside basic formatting.
Frequently Asked Questions
Does the JSON formatter work offline?⌄
Formatting and validation happen entirely in your browser — no data is sent to a server. It works without an internet connection once the page is loaded.
Is there a file size limit?⌄
The formatter handles JSON up to 10MB efficiently. Larger files may be slow to process in the browser.
Can I convert JSON to CSV or XML?⌄
JSON to CSV conversion is available for flat JSON arrays. JSON to XML conversion is on the roadmap.
Does it support JSON5 or JSONC (with comments)?⌄
Standard JSON only. JSON5 and JSONC variants are not supported.
Is it free?⌄
Yes. Completely free with no limits.
Try JSON Formatter — It's Free
No signup needed. 5 free uses daily. Pro plan from $9.99/month.
Open JSON Formatter →