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. To double-check a tricky payload, you can also run it through another online JSON validator.

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 parser's error message and, when the browser reports a position, the approximate line it's on.

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 the result automatically. Green means valid, with the document type and its top-level keys; red means invalid, with the parser's error message and the approximate line number when the browser gives one.

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 that an API response is valid JSON before your code tries to parse it. Handy when a proxy or error page sneaks HTML into what should be a JSON body.

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, single quotes, comments, or invalid characters. The validator shows the parser's error message and the approximate line. For the detailed syntax rules, check MDN's JSON documentation.

Does it validate JSON Schema?

No, this only checks syntax: does the text parse as JSON. It doesn't check a document against a schema, and it doesn't flag duplicate keys (JavaScript just keeps the last one). If you need a schema to start from, the JSON Schema Generator builds one from a sample. You can learn more about schemas 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 what the parser choked on and, usually, the line. Most of the time it's a missing comma, a trailing comma, or an unclosed bracket. The error is often reported just after the real mistake, so look at the line above too.

Related Tools

Other JSON tools you might find useful: