Check JSON Syntax
Validate JSON data and determine whether it follows standard JSON syntax rules.
DEVELOPER TOOL / JSON
Free Online JSON Validator
Check your JSON data for syntax errors with MoSanKit's free online JSON Validator. Paste your JSON, validate its structure and identify formatting issues such as missing commas, quotation marks or brackets in seconds.
✓ Quick, simple and free · No signup or installation required
JSON Validator workspace
PASTE JSON · VALIDATE · REVIEW ERRORS · FIX & RECHECK
Paste some JSON to get started.
JSON VALIDATION WORKSPACEMOSANKIT / DEVELOPER TOOLS
THE BASICS
What Is a JSON Validator?
A JSON Validator is a tool that checks whether JSON data follows the correct syntax and structure defined by the JSON format.
JSON requires specific formatting rules, including double-quoted property names, valid data types, correctly placed commas and matching brackets. Even a small syntax mistake can cause an application or API to reject the data.
A JSON Validator helps identify these errors so developers can correct their data before using it in applications.
BUILT FOR THE JOB
Key Features of MoSanKit JSON Validator
Identify Syntax Errors
Find common mistakes such as missing commas, unmatched brackets, invalid quotation marks and trailing commas.
Display Error Details
Show useful error messages and line or column information to help locate problems.
Validate Nested JSON
Check complex JSON structures containing nested objects, arrays and different data types.
Instant Validation
Validate JSON directly in your browser without sending data to an external server.
Copy and Recheck
Correct your JSON, validate it again and copy the updated content.
QUICK AND SIMPLE
How to Validate JSON Online
01 / ADD JSON
Paste your JSON
Enter or paste your JSON data into the input editor.
02 / VALIDATE
Click Validate JSON
Start the syntax validation process.
03 / REVIEW
Review the result
Check whether your JSON is valid or contains syntax errors.
04 / FIX & RECHECK
Fix and validate again
Correct the reported issues and run validation again.
COMMON MISTAKES
Common JSON Syntax Errors
Missing Commas
JSON requires commas between object properties and array elements, except after the final item.
Single Quotes Instead of Double Quotes
JSON property names and string values must use double quotation marks.
Trailing Commas
Standard JSON does not allow a comma after the final property or array element.
Unmatched Brackets
Every opening curly brace and square bracket must have a corresponding closing character.
Invalid Data Types
JSON supports strings, numbers, booleans, null, objects and arrays. Other values, such as undefined, are not valid JSON.
WHY MOSANKIT
Why Use an Online JSON Validator?
Invalid JSON can cause errors when working with APIs, configuration files, databases and web applications. Finding these issues manually becomes difficult when the data contains multiple nested objects and arrays.
MoSanKit's JSON Validator makes it easier to check JSON syntax, locate common errors and prepare valid data for development and testing.
MADE FOR EVERYDAY DEVELOPMENT
Who Can Use This Tool?
Frontend DevelopersValidate API responses and application data.
Backend DevelopersCheck JSON payloads and configuration files.
API DevelopersVerify request and response data.
QA EngineersValidate JSON during application testing.
StudentsLearn JSON syntax and structure.
GOOD TO KNOW
A few things, answered.
Quick answers about using the MoSanKit JSON Validator.
Yes. You can validate JSON online for free without creating an account.
Paste your JSON into the input editor and click Validate JSON. The tool checks its syntax and displays the validation result.
The validator displays an error message to help identify the syntax issue. You can correct the data and validate it again.
No. Standard JSON requires double quotes around property names and string values.
No. Standard JSON does not allow trailing commas after the final property or array element.
JSON supports strings, numbers, booleans, null, objects and arrays.
If validation runs entirely in your browser, your JSON data does not need to be uploaded to an external server.
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Catch JSON errors before
they affect your application.
Use MoSanKit's free online developer tools to format, validate and work with code more efficiently.