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JSON Parser & Validator — Beautify, Minify & Validate JSON

Free online JSON parser with real-time validation, beautify, minify, syntax highlighting, and precise error reporting. Paste JSON to format instantly.

Input

Ready

Output

// Output will appear here...
No errors
0 bytes

Why Is My JSON Invalid?

You pasted JSON from a terminal output, an API response, or a log file and got a cryptic "Unexpected token" error. The problem is usually one of five things: a missing comma between properties, a trailing comma after the last property, a mismatched bracket or brace, unquoted keys, or single quotes instead of double quotes. This tool pinpoints the exact line and column so you can fix the issue in seconds.

Real-time validation catches errors as you type. The byte count display helps you stay within API payload limits. The beautify and minify buttons let you switch between human-readable and compact formats for different stages of your workflow.

Common JSON Syntax Errors

Error Example Fix
Trailing comma { "a": 1, "b": 2, } Remove comma after last property
Unquoted keys { name: "Alice" } Use { "name": "Alice" }
Single quotes { 'name': 'Alice' } Use double quotes for keys and strings
Comments // this is not valid JSON Remove all comments
Missing comma { "a": 1 "b": 2 } Add comma between properties

Practical Examples

GitHub API response (minified from curl): 

{"login":"octocat","id":1,"avatar_url":"https://github.com/images/error/octocat_happy.gif","name":"The Octocat","public_repos":8}

Paste into the tool, click Beautify: 

{
  "login": "octocat",
  "id": 1,
  "avatar_url": "https://github.com/images/error/octocat_happy.gif",
  "name": "The Octocat",
  "public_repos": 8
}

Stripe webhook payload (common source of parsing errors): 

{
  "id": "evt_1234567890",
  "type": "payment_intent.succeeded",
  "data": {
    "object": {
      "id": "pi_3xyz",
      "amount": 2000,
      "currency": "usd"
    }
  }
}

Debugging Workflow

  1. Paste your JSON into the input panel. Validation runs automatically.
  2. If invalid, read the error message. It shows the exact line and column where the parser stopped.
  3. Go to that location in your source. Check for missing commas, unmatched brackets, or trailing commas.
  4. Fix the error and paste again. The tool re-validates in real time.
  5. Once valid, click Beautify to format for readability or Minify for storage.
  6. Check the byte count to verify your payload stays within API limits.

When to Use Each Feature

  • Beautify when reviewing API responses, debugging config files, or sharing JSON with teammates
  • Minify when preparing payloads for network transfer or reducing log file size
  • Byte count when checking payload size before sending to an API with strict limits
  • File upload when validating large configuration files or database exports
  • Copy/Download when exporting validated JSON to a file or clipboard

Limitations

  • Validates syntax only. For structural validation (required fields, data types), use JSON Schema with a dedicated validator.
  • Does not support JSON5, JSONC, or JSON with comments. Standard JSON requires double quotes and no comments.
  • File upload limited to 10MB to prevent browser memory issues.
  • Numbers beyond 2^53 may lose precision due to JavaScript's number type.

Frequently Asked Questions

Why does my JSON show "Unexpected token"?

This usually means a missing comma, trailing comma, or mismatched bracket. Check the line number in the error message and look at the preceding line. Trailing commas (a comma after the last property) are the most common cause.

Why won't my API response parse?

API responses sometimes include BOM characters, trailing commas from debug output, or non-JSON content like HTML error pages. Copy the raw response body (not the formatted view) and paste it. If the response starts with a BOM, remove the first character.

What's the difference between parsing and validation?

Parsing checks if the text follows JSON syntax rules (correct brackets, quotes, commas). Validation checks if the data matches a schema (required fields, correct types, value ranges). This tool does parsing. For schema validation, use a JSON Schema validator.

Does it handle large JSON files?

Files up to 10MB are supported via upload. Larger files may slow the browser. For very large datasets, consider streaming parsers or command-line tools like jq.

Why is trailing comma invalid?

The JSON specification (RFC 8259) does not allow trailing commas. Unlike JavaScript object literals, JSON is stricter. Many APIs reject payloads with trailing commas. This tool enforces the standard.

Is my data sent to a server?

No. All parsing happens in your browser. Nothing is transmitted to any server. You can disconnect from the internet and the tool still works.

Next Steps