Mastering JSON Schema: How to Validate API Responses

Imagine you're building a checkout form. You expect the price to be a number: "price": 19.99.

One day, the backend changes. Now it returns a string: "price": "19.99".

Suddenly, your math calculations break. total + price becomes "10" + "19.99" = "1019.99" instead of 29.99. Your users are confused, and your accounting is a mess.

This is why you need JSON Schema.

What is JSON Schema?

JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. It acts as a contract between the data provider (API) and the data consumer (Client).

It defines:

• Required fields (e.g., id must exist)
• Data types (e.g., age must be an integer)
• Formats (e.g., email must look like an email)
• Constraints (e.g., rating must be between 1 and 5)

How Validation Works

You have two JSON objects:

1. The Data: Your actual JSON content.
2. The Schema: The rulebook.

A validator compares them. If the data breaks any rule, it throws an error.

Example Schema:

json{
  "type": "object",
  "properties": {
    "name": { "type": "string" },
    "age": { "type": "integer", "minimum": 0 }
  },
  "required": ["name"]
}

• Valid Data: {"name": "Alice", "age": 25} ✅
• Invalid Data: {"age": 25} ❌ (Missing required 'name')
• Invalid Data: {"name": "Alice", "age": -5} ❌ (Age below minimum)

Why Use an Online Validator?

Writing schemas is tricky. A single typo in the schema definition can invalidate everything.

Our JSON Schema Validator allows you to:

1. Paste your Schema on the left.
2. Paste your JSON on the right.
3. Validate Instantly. See success or detailed error messages immediately.

It's perfect for:

• Testing new schemas before implementing them in code.
• Debugging why an API response is failing validation.
• Learning JSON Schema syntax with instant feedback.

Secure & Private

Like all our tools, the validation happens in your browser. Your API specs and data are never uploaded to the cloud.

Start Validating Today

Don't guess if your data is correct. Prove it.