JSON Validator Online

What Is a JSON Validator?

A JSON validator checks whether text follows the syntax rules of JSON (JavaScript Object Notation). JSON is a common format for exchanging structured data between applications, APIs, and services. A validator parses the text and reports whether its structure is valid JSON, helping you catch mistakes before using the data in a request, configuration, or program.

The RomitJSON JSON Validator checks syntax such as quoted property names, commas, brackets, braces, string escapes, and supported values. If the input is invalid, the result may include an error category, a parser message, and a line or column when the browser provides a useful location. Fix the indicated syntax and validate the JSON again.

Syntax validation checks that the document can be parsed as JSON. It does not confirm that the document contains every field your application expects, or that the values meet your business rules. Use JSON Schema or application-specific checks when you need to verify structure and meaning.

How to Validate JSON Online

1. Paste JSON into the input editor, or select Open JSON to choose a .json file.
2. Leave Live validation enabled to check smaller edits automatically. You can also select Validate JSON to start a manual check.
3. Review the result. Valid input is marked Valid JSON; invalid input includes an error explanation and location when available.
4. Correct the syntax in the editor, then run validation again to confirm the document parses.
5. If the document must follow a particular structure, check it with an appropriate JSON Schema Validator as a separate step.

Live validation pauses for inputs larger than 1 MiB so that editing remains responsive. Select Validate JSON to check those inputs manually. The validator accepts input up to 50 MiB. You can also load a sample to see the result format, clear the editor, copy the input, or download it as a JSON file.

Common JSON Syntax Errors

JSON has a strict syntax. A small typo can make an otherwise useful document invalid. These examples show frequent problems and how to correct them.

1. Missing commas between properties or values

Use a comma between each property in an object and between each item in an array. Do not omit the comma between adjacent entries.

Invalid JSON

{
  "name": "Aarav"
  "role": "Developer"
}

Correct JSON

{
  "name": "Aarav",
  "role": "Developer"
}

The missing comma belongs after the value "Aarav".

2. Single quotes instead of double quotes

JSON requires double quotation marks around property names and string values. Single-quoted strings that work in some programming languages are not valid JSON.

Invalid JSON

{'city': 'Patna'}

Correct JSON

{"city": "Patna"}

3. Trailing commas

A comma separates entries, so it cannot follow the last property in an object or the last item in an array.

Invalid JSON

{"name": "Aarav",}

Correct JSON

{"name": "Aarav"}

Remove the comma immediately before the closing brace or bracket.

4. Missing or mismatched braces and brackets

Every object opened with { must close with }, and every array opened with [ must close with ]. Nested structures need a matching closing character for each opening character.

Invalid JSON

{
  "skills": ["JavaScript", "HTML"
}

Correct JSON

{
  "skills": ["JavaScript", "HTML"]
}

5. Invalid values and capitalization

JSON values can be strings, numbers, objects, arrays, the lowercase Boolean literals true and false, or null. Capitalized values from other languages, such as Python's True or None, are not JSON values.

Invalid JSON

{
  "active": True,
  "nickname": None
}

Correct JSON

{
  "active": true,
  "nickname": null
}

JavaScript's undefined and the non-standard numeric values NaN and Infinity are not valid JSON values either. Use a supported JSON value instead.

6. Incorrect string escaping

Strings begin and end with double quotes. To include a double quote or a backslash inside a string, escape it with a backslash. JSON also supports escapes such as \n for a line break and \t for a tab.

Invalid JSON

{"message": "He said "hello""}

Correct JSON

{"message": "He said \"hello\""}

The \" sequence represents a quotation mark inside a JSON string.

7. Comments and invalid number formats

Standard JSON does not support line comments, block comments, or leading zeros on ordinary numbers. A value such as 007 must be written as 7. If a configuration format needs comments, check whether the consuming tool accepts an extension such as JSONC; JSONC is not standard JSON.

Invalid JSON

{
  "port": 3000, // server port
  "code": 007
}

Correct JSON

{
  "port": 3000,
  "code": 7
}

JSON Syntax Rules to Remember

• Write object property names and string values in double quotes.
• Separate properties and array items with commas, without a comma after the final entry.
• Use a colon between each property name and its value.
• Close every object and array with the matching brace or bracket.
• Write true, false, and null in lowercase.
• Escape quotation marks, backslashes, and control characters inside strings.
• Use valid JSON number syntax; do not use leading zeros, NaN, or Infinity.
• A JSON document may have an object, array, string, number, Boolean, or null as its top-level value.

JSON Validator vs. JSON Formatter vs. JSON Schema Validator

These tools address different steps in working with JSON. A JSON validator checks whether text follows JSON syntax. A JSON formatter makes valid JSON easier to read. A JSON Schema Validator checks whether a valid JSON document matches defined structural rules.

Use the JSON Formatter to improve readability, the JSON Viewer to inspect nested data, or the JSON Schema Validator to check a document against a schema.

If the input contains common JSON-like syntax mistakes, JSON Repair can attempt supported corrections. Review repaired output carefully before using it, because automatic repair may not know the intended meaning of your data.

How to Troubleshoot a JSON Validation Error

Start with the error category and parser message. If the validator reports a line or column, inspect that position and the nearby text. Some parsers point to where they detected a problem, which may be just after the character or value that caused it.

• For an error near a closing brace or bracket, look for a missing value, an extra comma, or a structure that was not closed.
• For an error near a property name, check for double quotes and a colon before the value.
• For an error inside a string, check the opening and closing quotes and escape any internal quotation marks or backslashes.
• For an error near a Boolean or null value, check spelling and lowercase capitalization.
• After fixing the first reported issue, validate again. One syntax error can hide later errors until it is corrected.

A valid JSON result confirms syntax only. If the application still rejects the data, check the expected property names, required fields, value types, and allowed ranges. Those requirements belong to the application or its schema.

Frequently Asked Questions

Related JSON Tools

Use this JSON validator to check syntax, then choose the next tool for your task: format valid data with the JSON Formatter, inspect nested structures with the JSON Viewer, check data rules with the JSON Schema Validator, or explore other options in the JSON toolbox.