JSON Validator Online - How to Validate JSON and Find Errors

What Is JSON Validation?

JSON validation is the process of checking whether a JSON document follows the syntax rules of the JSON format.

A valid JSON document can be parsed by software that supports JSON. An invalid JSON document contains one or more syntax problems that prevent it from being parsed correctly.

How to Validate JSON Online

The easiest way to check JSON is to use an online JSON validator. You can paste your JSON into the validator and check whether the structure is valid.

1. Open the HoxTools JSON Validator.
2. Paste your JSON into the input area.
3. Run the validation.
4. Check the result for syntax errors.
5. Correct the JSON and validate it again.

Valid JSON Example

The following is a simple example of valid JSON:

{
  "name": "John",
  "age": 30,
  "active": true
}

This JSON contains an object with three properties. Property names and string values use double quotation marks, and the values use valid JSON types.

Invalid JSON Example

The following example is invalid because the property name is not enclosed in double quotation marks:

{
  name: "John",
  "age": 30
}

Standard JSON requires object property names to be enclosed in double quotation marks.

Common JSON Errors

Many JSON problems are caused by a small number of common syntax mistakes. Understanding these mistakes can make debugging much easier.

1. Missing Commas

JSON properties in an object normally need to be separated by commas.

{
  "name": "John"
  "age": 30
}

A comma is missing after the "John" value.

2. Using Single Quotes

Standard JSON strings use double quotation marks, not single quotation marks.

{
  'name': 'John'
}

The correct version is:

{
  "name": "John"
}

3. Trailing Commas

A trailing comma after the last property or array item is not valid in standard JSON.

{
  "name": "John",
  "age": 30,
}

Remove the comma after the final value.

4. Unmatched Brackets

JSON objects use curly brackets and arrays use square brackets. Opening and closing brackets must match correctly.

{
  "products": [
    "Phone",
    "Cover"
}

The array and object are not properly closed in this example.

5. Invalid Boolean Values

JSON uses the lowercase values true and false.

{
  "active": True
}

The correct JSON value is:

{
  "active": true
}

6. Comments in JSON

Standard JSON does not support comments.

{
  "name": "John"
  // This is a comment
}

If comments are required by a particular configuration format, that format may use an extension or a different syntax. Standard JSON itself does not include comments.

7. Incorrect Number Formatting

JSON numbers have specific syntax rules. For example, a number such as 01 is not valid standard JSON because JSON does not allow unnecessary leading zeros.

{
  "number": 01
}

Use:

{
  "number": 1
}

JSON Validator vs JSON Formatter

A JSON validator and JSON formatter perform different jobs, although they are often used together.

• JSON Validator: checks whether JSON follows valid syntax.
• JSON Formatter: makes JSON easier to read by adding indentation and line breaks.

If your JSON is difficult to read but valid, a formatter can improve readability. If you are receiving a parsing error, a validator can help identify a syntax problem.

Why JSON Validation Is Important for APIs

APIs frequently exchange information using JSON. A client application may send JSON to a server, and the server may return JSON in response.

If the JSON is malformed, the receiving application may fail to parse the request or response.

Developers commonly validate JSON while creating or debugging API requests, configuration files and application data.

JSON Validation for Developers

Developers may encounter JSON in many different situations, including:

• REST APIs
• Web applications
• Mobile applications
• Configuration files
• Database exports
• API testing
• JavaScript applications
• Data exchange between applications

When an application reports a JSON parsing error, checking the JSON independently can help determine whether the problem is caused by the JSON syntax.

How to Fix Invalid JSON

When JSON validation reports an error, review the structure carefully. The following checklist can help:

1. Check that property names use double quotation marks.
2. Check that strings use double quotation marks.
3. Check commas between properties and array items.
4. Remove trailing commas.
5. Check opening and closing brackets.
6. Check that boolean values are lowercase.
7. Remove comments from standard JSON.
8. Check number formatting.
9. Validate the JSON again after making changes.

Validation Does Not Check Business Logic

An important distinction is that syntactically valid JSON can still contain incorrect information.

Therefore, JSON validation is only one part of checking data. Applications may also need to perform data type, range, required-field and business-rule validation.

JSON Validation and Security

For ordinary JSON that does not contain sensitive information, an online validator can be a convenient way to check syntax quickly.

Can JSON Validation Automatically Fix Errors?

Validation and correction are different tasks. A validator identifies whether JSON is valid and may report an error, but automatically fixing malformed JSON can be risky because there may be multiple possible interpretations of the intended structure.

For reliable results, review the reported problem and correct the JSON according to the data you actually intend to send or store.

JSON Validator Online at HoxTools

HoxTools provides a free online JSON Validator for checking JSON syntax directly in your browser.

You can use it when working with API responses, development projects, configuration data or any other non-sensitive JSON that you need to check.

Related HoxTools

• JSON Validator
• JSON Formatter
• Base64 Encoder & Decoder
• URL Encoder & Decoder
• JSON Formatter Online Guide
• All Free Online Tools

Frequently Asked Questions

Conclusion

JSON validation is useful whenever you need to confirm that JSON follows the standard syntax rules before using it in an application, API or configuration file.

Checking commas, quotation marks, brackets, values and other syntax rules can help you quickly identify common JSON problems. For an easier workflow, you can validate JSON first and then format valid JSON for better readability.