JSON FormatterFormat and validate JSON locally
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JSON Formatter and Validator

Format, validate, and inspect JSON locally in your browser with copyable pretty-printed output. No uploads.

Output
{
  "hello": "world"
}

Quick answer

This JSON formatter turns minified or messy JSON into readable, indented output and validates the text with the browser JSON parser. It is useful for API responses, configuration snippets, structured logs, and examples that should stay on your device.

How to use

  1. 1. Paste JSON textAdd an API response, configuration object, schema draft, or other JSON document in the input panel.
  2. 2. Review parse feedbackValid JSON is formatted immediately. Invalid JSON shows an inline error so you can fix quotes, commas, brackets, or unexpected values.
  3. 3. Copy the formatted resultUse the pretty-printed output for code review, debugging notes, documentation, or sharing in an issue.

Examples

Minified object

Input
{"status":"ok","items":[1,2,3]}
Output
{
  "status": "ok",
  "items": [
    1,
    2,
    3
  ]
}

Common validation issue

Input
{"name":"AppHelp",}
Output
Invalid JSON

Trailing commas are not valid JSON even though some JavaScript tools allow them.

Common use cases

  • Read compressed API payloads without sending private data to a formatter service
  • Validate configuration snippets before committing them
  • Clean up webhook, log, or test fixture JSON for documentation
  • Compare nested keys and arrays while debugging frontend or backend behavior

Edge cases

  • JSON requires double-quoted object keys and string values
  • Trailing commas, comments, NaN, Infinity, and undefined are JavaScript syntax, not valid JSON
  • Large files are limited by browser memory because formatting runs locally
  • Escaped JSON strings may need JSON String Escape / Unescape before they can be parsed as a document

Features

  • Format and beautify minified JSON
  • Validate JSON syntax with clear error messages
  • Two-pane layout for input and output
  • Runs entirely in the browser

Related tools

JSON String Escape / UnescapeConvert quoted string content before embedding it in JSON.JSON ValidatorCheck JSON validity with a focused validation workflow.JSON to CSVConvert structured JSON into tabular CSV.JSON Schema GeneratorGenerate a draft schema from sample JSON.

Frequently asked questions

Is this JSON formatter free?
Yes. AppHelp's JSON formatter is free, with no signup, no upload, and no ads.
Does my JSON leave my browser?
No. Parsing and formatting use the browser's built-in JSON.parse — nothing is uploaded.
How is invalid JSON reported?
An inline error message highlights the problem. Common issues like trailing commas and unquoted keys are flagged so you can fix them quickly.