JSON Validator
Validate and format JSON with detailed error messages
JSON Validation
Checks for syntax errors and formats valid JSON.
Free Online JSON Validator - Validate & Format JSON Instantly
Welcome to DevToolVault's free online JSON validator, your go-to tool for validating, debugging, and formatting JSON data. Whether you're working with API responses, configuration files, or data exports, our browser-based validator provides instant syntax checking with detailed error messages—all while keeping your data completely private.
Why JSON Validation Matters
JSON (JavaScript Object Notation) has become the universal language for data exchange on the web. APIs, configuration files, databases, and web applications all rely on properly formatted JSON. A single misplaced comma or unclosed bracket can break your entire application. Our validator catches these errors instantly, saving you hours of debugging time.
How to Use This JSON Validator
Simply paste your JSON into the input field and click "Validate JSON." If your JSON is valid, you'll see a green checkmark and a beautifully formatted (pretty-printed) version of your data. If there's an error, you'll get a detailed message indicating exactly what's wrong and where the parser encountered the issue.
JSON Syntax Rules
- Strings: Must be wrapped in double quotes ("), not single quotes
- Property Names: Must be strings in double quotes
- Values: Can be strings, numbers, booleans, null, arrays, or objects
- Arrays: Comma-separated values in square brackets []
- Objects: Key-value pairs in curly braces {}
- No Trailing Commas: Last item in arrays/objects cannot have a comma
- No Comments: Standard JSON doesn't support // or /* */ comments
Common JSON Validation Errors
The most frequent JSON errors include: unexpected tokens (often from trailing commas), unterminated strings (missing closing quotes), invalid escape sequences (use \\ for backslash), unexpected end of input (missing closing brackets), and using JavaScript literals like undefined or NaN which aren't valid JSON values.
Privacy-First JSON Validation
DevToolVault's JSON validator processes everything locally in your browser using JavaScript's native JSON.parse() function. Your data never leaves your device—no server uploads, no logs, no tracking. This makes it safe to validate sensitive API responses, configuration secrets, database exports, or any confidential JSON data.
JSON vs. Related Formats
While JSON is widely used, related formats serve different needs: YAML offers human-readable configuration with comments, TOML excels for simple configs, XML provides schema validation and namespaces, and Protocol Buffers offer efficient binary serialization. Our JSON to YAML converter helps you switch between these formats easily.
Frequently Asked Questions
What is JSON and why does it need validation?
JSON (JavaScript Object Notation) is a lightweight data interchange format. Validation ensures your JSON follows correct syntax rules—proper brackets, quotes, commas, and data types—preventing parsing errors in applications that consume the data.
What are common JSON syntax errors?
Common JSON errors include: trailing commas after the last item, single quotes instead of double quotes, unquoted property names, missing commas between elements, unclosed brackets or braces, and invalid escape sequences in strings.
What is the difference between JSON and JavaScript objects?
While similar, JSON is stricter: property names must be double-quoted strings, only allows strings, numbers, booleans, null, arrays, and objects (no functions, undefined, or dates), and doesn't support comments or trailing commas.
How do I format or beautify JSON?
Our tool automatically formats valid JSON with proper indentation (2 spaces). This "pretty printing" makes nested structures readable. For minified JSON, you can use tools that remove whitespace for smaller file sizes.
Can JSON contain comments?
Standard JSON does not support comments. If you need comments, consider using JSON5 (extended JSON), JSONC (JSON with Comments used by VS Code), YAML, or storing documentation in a separate file.
What is the maximum size of a JSON file?
JSON itself has no size limit, but practical limits depend on the parser. Browser JavaScript can typically handle files up to hundreds of megabytes. For very large datasets, consider streaming JSON parsers or formats like NDJSON.
Is my JSON data secure when validating here?
Absolutely! Our JSON validator processes everything in your browser using JavaScript's built-in JSON.parse(). No data is transmitted to servers. Your API responses, configurations, and sensitive data stay completely private.
How do I validate JSON against a schema?
JSON Schema validation checks that JSON data conforms to a defined structure. While our tool validates JSON syntax, schema validation requires additional tools like AJV or JSON Schema validators to verify data types, required fields, and constraints.
Related JSON Tools: Try our JSON/YAML Converter, JSON to JSONL Converter, and Code Formatter for more data transformation utilities.