JSON Formatter & Validator Online — Free Tool
Identify syntax errors in JSON objects and auto-format your data for optimal readability.
Indent
Valid JSON
Privacy note: All processing happens entirely in your browser. No data is sent to our servers.
About this tool
JSON must be syntactically valid for parsers to accept it. This tool pretty-prints with indentation and pinpoints errors like trailing commas, missing quotes, or bracket mismatches.
Paste API responses or config files to validate structure before commit or deploy.
Common use cases
- Debugging malformed API responses
- Cleaning minified config for code review
- Teaching nested object structure
- Validating webhook payloads in support tickets
How to use
- Paste minified or messy JSON into the editor.
- Run format or rely on auto-format if enabled.
- Read error messages if validation fails and fix line indicated.
- Copy pretty JSON into your project or ticket.
This page is available at /tools/json-formatter-validator/.
Understanding the result
- Valid JSON allows objects, arrays, strings, numbers, booleans, and null only—no comments or trailing commas in strict JSON.
- Indentation is cosmetic; parsers ignore whitespace.
- Large payloads may lag the editor—collapse sections mentally or split files.
- Unicode and escaped characters (\n, \uXXXX) decode in the parsed view.
Related tools
JSON to CSV Converter
Transform complex JSON arrays and nested objects into clean, exportable CSV files locally within your browser.
JSON to TypeScript Interface
Convert raw JSON payloads into strongly-typed TypeScript interfaces to accelerate development.
JSON to C# Model
Automatically generate C# POCO classes and data models from standard JSON objects.
JSON Table Viewer
Visualize and analyze raw JSON data through an interactive, searchable, and sortable data table interface.
Base64 Encoder & Decoder
Securely encode plain text into Base64 format, or decode Base64 strings back to their original readable state.
Border Radius Generator
Configure border radius attributes intuitively and generate the accompanying CSS or Tailwind classes.
FAQ
JSON vs JavaScript object?
JSON requires double quotes on keys and no trailing commas. JS objects are looser.
Why trailing comma error?
Standard JSON disallows trailing commas after last array/object element.
Can I minify JSON?
Yes if the tool offers compact mode—opposite of pretty-print.
Is data sent to server?
Browser formatters should process locally only.