Validate and format JSON data online with real-time error highlighting, line numbers, and syntax checking. Perfect for testing API responses, debugging configuration files, and ensuring valid JSON structure for web development projects.
Validate and check XML data online for syntax errors, proper structure, and well-formed markup. Essential for testing SOAP services, RSS feeds, configuration files, and ensuring valid XML documents for web services and data interchange.
Key Features of Our Free JSON and XML Validator
Instant Real-Time Validation
Get immediate validation results for your JSON and XML data with precise error messaging and syntax checking. No waiting, no uploads - validate instantly in your browser.
Syntax Error Highlighting & Line Numbers
See exactly where JSON and XML syntax errors occur with line numbers and clear visual indicators. Quickly identify and fix validation issues in your code.
100% Free and Secure Online Tool
All validation processing happens locally in your browser. Your JSON and XML data is never sent to or stored on our servers, ensuring complete privacy and security.
Format, Beautify & Minify JSON/XML
One-click formatting and beautification to make your JSON and XML code readable with proper indentation. Includes JSON minifier for compact output.
How to Use the JSON and XML Validator Tool
Paste Your JSON or XML Data
Copy and paste your JSON or XML code into the online editor panel. Use the example button to load sample JSON or XML data if you want to test the validator first.
Validate Your Code
Click the "Validate JSON" or "Validate XML" button to instantly check your data for syntax errors, structural issues, and proper formatting.
Review Validation Results
Check the validation results panel to see if your JSON or XML data is valid. If errors are found, they'll be highlighted in the editor with line numbers to help you fix syntax issues quickly.
Format, Copy & Download
Use the format button to beautify and properly indent your JSON or XML code. Then copy to clipboard or download the validated file for use in your development projects.
Who Uses JSON and XML Validators?
Our free online JSON validator and XML validator tools are essential for:
Web Developers & Software Engineers
Validate REST API payloads and responses, test JSON configurations, debug web service data, and ensure data correctness during software development and API integration.
Front-End Designers & UI Developers
Validate JSON configuration files, check SVG XML data, verify structured content for web applications, and ensure proper data formatting for React, Vue, and Angular applications.
Computer Science Students
Learn JSON and XML syntax, practice creating data structures, validate homework assignments, and get immediate feedback while studying web development, data interchange formats, and API design.
Data Analysts & Data Scientists
Validate data exports from databases, check API query results, verify JSON data from NoSQL databases like MongoDB, and ensure structured data integrity before processing, analysis, or import into data tools.
Understanding JSON and XML Validation: Complete Guide
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 validation has become essential for web development as JSON serves as the dominant format for REST APIs, configuration files, and data storage across programming languages including JavaScript, Python, Java, PHP, and Ruby. The JSON 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. Using a JSON validator ensures your data structure is properly formatted and error-free.
XML (Extensible Markup Language) provides a markup language for encoding documents readable by both humans and machines. Developed by the W3C, XML validation is crucial for ensuring well-formed documents. 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. An XML validator checks for proper syntax and structure. XML excels in scenarios requiring strict data validation through XSD (XML Schema Definition) or DTD (Document Type Definition), making XML validators essential for SOAP web services, configuration files, RSS feeds, and enterprise data exchange systems.
Common JSON Syntax Errors to Check with a Validator
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 Detected by Online Validators
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 Validator vs XML Validator: When to Use Each Format
Use JSON and a JSON Validator 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. Always validate JSON data to ensure proper formatting.
Use XML and an XML Validator 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. XML validators ensure compliance with strict data schemas.
JSON Validation in Modern Web 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 Validation 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 with XML validators.
Best Practices for JSON and XML Validation
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 When Validating JSON and XML
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.
JSON and XML Processing Libraries for Developers
JavaScript JSON/XML Validation: Native JSON.parse() and
JSON.stringify() for JSON validation and parsing. DOMParser, xml2js, and fast-xml-parser
libraries for XML validation and processing in Node.js and browser applications.
Python JSON/XML Validation: Built-in json module for JSON parsing and validation. lxml and ElementTree libraries for XML validation and processing. xmltodict package converts XML to Python dictionaries for easier data manipulation.
Java JSON/XML Validation: Jackson and Gson libraries for JSON parsing, validation, and serialization. JAXB for XML binding and validation. DOM, SAX, and StAX parsers provide different approaches to XML processing and validation in Java applications.
Frequently Asked Questions About JSON and XML Validation
What is a JSON validator? A JSON validator is an online tool or software that checks JSON data for syntax errors, proper formatting, and structural correctness. It ensures your JSON follows the official specification and can be parsed without errors by applications and APIs.
What is an XML validator? An XML validator is a tool that verifies XML documents are well-formed and valid according to XML syntax rules. It checks for proper tag nesting, attribute formatting, special character encoding, and optionally validates against schemas like XSD or DTD.
Why do I need to validate JSON? Validating JSON prevents runtime errors in applications, ensures API compatibility, catches syntax mistakes before deployment, and helps debug data structure issues. A JSON validator saves development time by identifying problems like missing commas, unclosed brackets, or incorrect quote usage.
Is this JSON/XML validator free to use? Yes, this online JSON and XML validator is completely free with no registration required. All validation happens in your browser, ensuring your data remains private and secure.
Can I validate large JSON or XML files? Yes, this validator can handle large JSON and XML files. Since validation occurs locally in your browser, the size limit depends on your browser's memory capacity. For extremely large files, consider using command-line validation tools.
Does the validator store my data? No, all JSON and XML validation happens entirely in your browser using JavaScript. Your data is never uploaded to servers or stored anywhere, ensuring complete privacy and security for sensitive information.
What's the difference between JSON and XML? JSON is a lightweight data format using key-value pairs, ideal for web APIs and JavaScript applications. XML is a markup language with tags and attributes, better suited for document-centric data and enterprise systems requiring strict schema validation.
Can I format minified JSON? Yes, use the Format button to beautify minified or compact JSON. The validator will add proper indentation and line breaks, making the code readable. You can also minify formatted JSON using the Minify button for compact transmission.