JSON Quiz Test Online (30 random Questions) 2026

This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various JSON topics, including the introduction to JSON, JSON syntax and basics, data types, operations in JavaScript, APIs and JSON, advanced structures, JSON Schema, tools and debugging, as well as performance and security considerations. Whether you’re new to JSON or looking to refine your skills, this quiz will enhance your understanding of JSON’s role in modern web development.

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30 Minutes JSON Quiz Test Online

Welcome to the JSON Quiz! This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various JSON topics, including the introduction to JSON, JSON syntax and basics, data types, operations in JavaScript, APIs and JSON, advanced structures, JSON Schema, tools and debugging, as well as performance and security considerations. Whether you're new to JSON or looking to refine your skills, this quiz will enhance your understanding of JSON's role in modern web development.

1 / 30

1. How are floating-point numbers represented in JSON?

A) 1.23f

B) "1.23"

C) float(1.23)

D) 1.23

2 / 30

2. What is the effect of caching JSON responses?

A) Increases JSON size

B) Converts JSON to binary format

C) Reduces server processing time for repeated requests

D) Prevents JSON injection attacks

3 / 30

3. What is a common format for API error responses?

A) XML document

B) Plain text

C) CSV file

D) JSON object

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4. JSON is a strict subset of which language?

A) SQL

B) XML

C) Python

D) JavaScript

5 / 30

5. What is JSON primarily used for?

A) Styling web pages

B) Creating animations

C) Data exchange between a client and a server

D) Sending emails

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6. What is the default HTTP method for the fetch() function?

A) GET

B) POST

C) PUT

D) PATCH

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7. What is the use of the $ref keyword in JSON Schema?

A) To reference external files

B) To specify required properties

C) To define a default value

D) To include reusable schema definitions

8 / 30

8. Which data structure is JSON closest to?

A) Key-value store

B) Relational tables

C) Arrays

D) Trees

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9. What data type is represented by {} in JSON?

A) Object

B) String

C) Array

D) Null

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10. What does a JSON compressor do?

A) Converts JSON to XML

B) Removes unnecessary whitespace for smaller size

C) Validates JSON

D) Beautifies JSON

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11. Which data structure is not directly supported by JSON?

A) Array

B) Set

C) Object

D) String

12 / 30

12. What will JSON.stringify(true) return?

A) "true"

B) Throws an error

C) true

D) "True"

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13. Which of the following ensures JSON data is safe from injection attacks?

A) Removing all keys from JSON

B) Input validation and sanitization

C) Using only numeric data

D) Minification

14 / 30

14. Which keyword restricts the number of items in a JSON array?

A) maxSize

B) minLength

C) arrayLimit

D) maxItems

15 / 30

15. Which testing tools commonly use JSON for request and response data?

A) Postman and JMeter

B) Figma and Sketch

C) Jenkins and Kubernetes

D) Selenium and Puppeteer

16 / 30

16. Which keyword specifies the schema for items in a JSON array?

A) type

B) definitions

C) properties

D) items

17 / 30

17. What is the output of JSON.parse('[1, 2, , 4]')?

A) [1, 2, null, 4]

B) Throws a SyntaxError

C) [1, 2, undefined, 4]

D) [1, 2, , 4]

18 / 30

18. How do you access the second element of a JSON array ["apple", "banana", "cherry"]?

A) array.get(1)

B) array["banana"]

C) array.index(1)

D) array[1]

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19. Which JSON data type is used to represent a collection of items?

A) Object

B) Number

C) Array

D) String

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20. What is a safe alternative to eval() for parsing JSON in JavaScript?

A) JSON.minify()

B) JSON.stringify()

C) JSON.debug()

D) JSON.parse()

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21. What can be the root structure of a JSON document?

A) A string

B) Either an object or an array

C) Only an object

D) Only an array

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22. What does the oneOf keyword do in JSON Schema?

A) Requires all listed schemas to match

B) Validates against one specific type

C) Combines multiple schemas

D) Ensures that the data matches exactly one of the specified schemas

23 / 30

23. What happens when duplicate keys are present in a JSON object?

A) The last key-value pair overrides the previous ones

B) An error is thrown

C) Both key-value pairs are stored

D) The first key-value pair is ignored

24 / 30

24. Which of these is a valid JSON string?

A) 'Hello, World!'

B) (Hello, World!)

C) "Hello, World!"

D) Hello, World!

25 / 30

25. What is the most efficient way to handle large JSON datasets in memory-constrained environments?

A) Convert JSON to XML first

B) Use streaming APIs to process JSON incrementally

C) Load the entire JSON at once

D) Remove all nested objects

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26. How do you check if a given JavaScript object is a valid JSON object?

A) Use Object.prototype.toString()

B) Use Array.isArray()

C) Use typeof to check if it is an object

D) Convert it to a string using JSON.stringify() and back using JSON.parse()

27 / 30

27. How can JSON responses be protected from being cached by unauthorized users?

A) Convert JSON to XML

B) Minify the JSON data

C) Use the Cache-Control header with no-store

D) Use large nested objects

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28. How do you specify that a JSON object must have at least one key in JSON Schema?

A) minItems: 1

B) minKeys: 1

C) minProperties: 1

D) required: true

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29. What is the output of JSON.stringify() on a nested object?

A) Throws an error

B) A flattened version of the object

C) A deep copy of the object

D) A string representation of the nested object

30 / 30

30. Can JSON keys have spaces?

A) Yes, with quotes

B) Yes, without quotes

C) Only in arrays

D) No

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