Validate and format JSON data with error highlighting and line numbers.
Validate and check XML data for syntax errors and proper structure.
Features of Our Validator Tool
Instant Feedback
Get immediate results for your JSON and XML data validation with precise error messaging.
Error Highlighting
See exactly where errors occur with line numbers and clear visual indicators.
Free and Secure
All processing happens in your browser , no data is sent to or stored on our servers.
Format and Beautify
One-click formatting to make your code readable and properly indented.
How to Use the Validator
Paste Your Data
Copy your JSON or XML data into the respective editor panel. Use the example button if you need sample data.
Click Validate
Press the "Validate" button to check your data for syntax errors and proper structure.
Review Results
Check the results panel to see if your data is valid or if it contains errors. Fix any errors highlighted in the editor.
Format and Export
Use the format button to beautify your code, then copy or download it for your projects.
When to Use This Tool
Our JSON and XML validators are perfect for:
Developers
Testing API payloads, responses, and ensuring data correctness during development.
Web Designers
Validating configuration files, SVG data, and structured content for web applications.
Students
Learning JSON or XML syntax and practicing data structure creation with immediate feedback.
Data Analysts
Checking data exports, API results, and structured data before processing or import.
Understanding JSON and XML Data Formats
JSON (JavaScript Object Notation) is a lightweight data interchange format that humans can easily read and machines can easily parse. Originally specified by Douglas Crockford in the early 2000s, JSON has become the dominant format for web APIs, configuration files, and data storage across programming languages including JavaScript, Python, Java, PHP, and Ruby. The syntax uses key-value pairs enclosed in curly braces for objects and square brackets for arrays, with keys as strings in double quotes and values as strings, numbers, booleans, null, arrays, or nested objects.
XML (Extensible Markup Language) provides a markup language for encoding documents readable by both humans and machines. Developed by the W3C, XML uses tags enclosed in angle brackets similar to HTML, with opening tags, closing tags, and optional attributes. XML documents follow a hierarchical tree structure with a single root element containing child elements. XML excels in scenarios requiring strict data validation through XSD (XML Schema Definition) or DTD (Document Type Definition), making it popular for SOAP web services, configuration files, RSS feeds, and enterprise data exchange.
Common JSON Syntax Errors
Missing or Extra Commas: Valid JSON requires commas separating all items except the final one. {"name": "John", "age": 30} is correct, while {"name": "John" "age": 30} (missing comma) and {"name": "John", "age": 30,} (trailing comma) are invalid.
Incorrect Quote Usage: JSON strictly requires double quotes for strings and property names. Single quotes cause validation errors. {"name": "value"} works while {name: "value"} or {'name': "value"} do not.
Unclosed Brackets: Every opening bracket [ or brace { requires a matching closing character. Missing closures leave structures incomplete, causing parsers to fail.
Invalid Data Types: JSON supports only strings, numbers, booleans, null, objects, and arrays. Date values must be strings in ISO 8601 format like "2024-01-15T10:30:00Z".
Common XML Syntax Errors
Missing Closing Tags: Every opening tag like <title> requires a corresponding closing tag </title>. Self-closing tags use <element /> syntax.
Improper Nesting: Child elements must be completely contained within parent elements. <parent><child>content</child></parent> is valid, while overlapping tags fail validation.
Special Characters: XML reserves < > & and quotes. Use < > & ' " entity references to escape these characters.
Invalid Attributes: Attribute values must be quoted. <element attribute="value"> is valid, while <element attribute=value> fails.
JSON vs XML: When to Use Each
Use JSON When: Your application requires fast parsing, minimal bandwidth, and works with REST APIs, NoSQL databases like MongoDB, or JavaScript-heavy applications. Modern web APIs from Twitter, Facebook, and Google deliver JSON by default.
Use XML When: You need rigorous schema validation through XSD, formal contracts between systems, or work with SOAP web services, Microsoft Office formats (DOCX, XLSX), or industry standards like HL7 for healthcare.
JSON in Modern Development
REST APIs have standardized on JSON for request and response payloads. React and Vue applications fetch data using JSON.parse() or the Fetch API. Package managers use JSON configuration files extensively, including package.json for Node.js, tsconfig.json for TypeScript, and .eslintrc for ESLint. NoSQL databases like MongoDB store records as BSON (Binary JSON), with developers querying using JSON-style objects.
XML in Enterprise Systems
SOAP web services use XML exclusively for message formatting, defined through WSDL files. Java enterprise applications rely on XML for Spring Framework bean configurations, Maven pom.xml dependencies, and Hibernate ORM mappings. Industry standards like HL7 for healthcare and ACORD for insurance use XML for data interchange requiring formal validation.
Best Practices
JSON: Use consistent formatting (2 or 4 space indentation), validate during development with ESLint, implement JSON Schema validation, escape special characters properly, keep arrays homogeneous, and use meaningful property names like camelCase or snake_case.
XML: Include single root element, use proper nesting, implement XSD schema validation, use CDATA sections for complex content, choose elements for data and attributes for metadata, include comments for documentation, and validate against multiple parsers.
Security Considerations
JSON Injection: Always escape user input before including in JSON. Use proper serialization libraries that handle escaping automatically rather than concatenating strings manually.
XML External Entity (XXE): Disable external entity processing in XML parsers when handling untrusted input. Modern parsers typically disable this by default, but verify settings.
Denial of Service: Implement limits on document size, parsing depth, and expansion ratios. The "billion laughs attack" uses nested entities expanding into gigabytes of data.
Processing Libraries
JavaScript: Native JSON.parse() and JSON.stringify() for JSON. DOMParser, xml2js, and fast-xml-parser for XML.
Python: Built-in json module for JSON. lxml and ElementTree for XML. xmltodict converts XML to dictionaries.
Java: Jackson and Gson for JSON. JAXB for XML binding. DOM, SAX, and StAX parsers for different XML processing styles.