JSON Validator
Validate JSON syntax and check for errors
JSON Input
Validation Result
What is JSON Validator?
A simple tool to check if your JSON is valid or broken. Paste your JSON, upload a file, or try the sample data – you'll see right away if there are any syntax errors.
Uses JavaScript's built-in JSON parser following the RFC 8259 JSON specification, so it follows the same rules as your code. According to ECMA-404, the standard for JSON data interchange format, proper validation prevents runtime errors. Everything runs locally in your browser – nothing gets sent to any server.
Features
Real-time Validation
Checks your JSON as you type. Green badge means it's valid, red means there's an error.
Error Details
Shows the line number and what went wrong. Makes debugging way easier.
File Upload
Upload JSON files directly instead of copy-pasting everything.
Sample Data
Try the sample buttons to see valid and invalid examples.
Syntax Highlighting
Color-coded JSON makes it easier to spot issues visually.
Local Processing
Everything runs in your browser. Your data stays on your machine.
How to Use
Add Your JSON
Paste JSON into the left editor, upload a file, or click one of the sample buttons to try it out.
Check Results
The right panel shows validation results automatically. Green = valid, red = has errors. Error messages include line numbers.
Fix Issues
Use the error details to fix problems. Usually it's missing commas, unclosed brackets, or trailing commas. The validator updates as you fix things.
Use Cases
API Responses
Quick check if an API response is valid JSON before your code tries to parse it. Essential for REST API development and testing.
Config Files
Validate JSON config files before deployment. One typo can break everything.
Learning
If you're new to JSON, use this to check your work and see what errors look like.
Debugging
Getting parse errors? Validate the JSON first to find the exact problem.
FAQ
Is my data stored?
No. Everything runs in your browser using JSON.parse(). Nothing gets sent anywhere.
What makes JSON invalid?
Missing commas, trailing commas, unclosed brackets, unquoted keys, or invalid characters. The validator will tell you exactly what's wrong. For detailed syntax rules, check MDN's JSON documentation.
Does it validate JSON Schema?
No, this only checks syntax. For schema validation, try the JSON Schema Generator. Learn more about JSON Schema at json-schema.org.
Can I validate large files?
Yes, but performance depends on your browser. Small files are instant. Very large files (10MB+) might take a moment.
Why is my JSON invalid?
Check the error message – it shows the line and what's wrong. Usually it's missing commas, trailing commas, or unclosed brackets.
Related Tools
Other JSON tools you might find useful:
For more about JSON best practices, read the Google JSON Style Guide.