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. What is the correct syntax for a JSON object?

A) {"key": "value"}

B) {key: "value"}

C) [key: "value"]

D) {key = "value"}

2 / 30

2. Why should large JSON files be paginated in APIs?

A) To avoid key duplication

B) To increase readability

C) To reduce client-side processing time

D) To improve network performance and reduce latency

3 / 30

3. Which keyword defines a numeric range in JSON Schema?

A) min and max

B) minimum and maximum

C) numberRange

D) range

4 / 30

4. How are elements in a JSON array separated?

A) Semicolons

B) Colons

C) Commas

D) Dots

5 / 30

5. What is the purpose of JSON in REST APIs?

A) To define API endpoints

B) To render HTML pages

C) To structure and exchange data between client and server

D) To validate API responses

6 / 30

6. What happens if a JSON object has circular references when using JSON.stringify()?

A) It converts successfully

B) It skips the circular reference and continues

C) It throws a TypeError

D) It returns an empty object

7 / 30

7. What is the difference between allOf and oneOf in JSON Schema?

A) allOf is for strings, oneOf is for arrays

B) allOf allows duplicates, oneOf does not

C) allOf validates all schemas, oneOf validates only one schema

D) oneOf requires at least one match, allOf requires none

8 / 30

8. Which function can convert an API response from JSON to JavaScript objects?

A) response.json()

B) JSON.stringify()

C) JSON.decode()

D) response.parse()

9 / 30

9. What is the MIME type for JSON?

A) text/json

B) application/json

C) text/plain

D) application/javascript

10 / 30

10. What is the purpose of the dependencies keyword in JSON Schema?

A) To validate nested objects

B) To define key dependencies

C) To define type constraints

D) To specify default values

11 / 30

11. Which of the following JSON data types is valid?

A) All of the above

B) Object

C) Float

D) String

12 / 30

12. Which tool is used to validate JSON syntax?

A) XMLParser

B) JSONParser

C) JSONLint

D) Postman

13 / 30

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

A) Postman and JMeter

B) Selenium and Puppeteer

C) Jenkins and Kubernetes

D) Figma and Sketch

14 / 30

14. How can large nested JSON objects impact performance?

A) They make JSON more secure

B) They slow down parsing and increase memory usage

C) They reduce API latency

D) They improve network speed

15 / 30

15. What is the primary function of JSON.stringify(value, replacer, space)?

A) Converts JSON to XML

B) Beautifies JSON output

C) Compresses JSON output

D) Converts an object to a string with formatting options

16 / 30

16. Which of the following is a commonly used library for making API requests in JavaScript?

A) jQuery

B) D3.js

C) Lodash

D) Axios

17 / 30

17. Which of the following is NOT a supported data type in JSON?

A) String

B) Undefined

C) Number

D) Boolean

18 / 30

18. Which keyword in JSON Schema defines the type of a value?

A) type

B) format

C) properties

D) items

19 / 30

19. What is the typical file extension for JSON files?

A) .xml

B) .js

C) .txt

D) .json

20 / 30

20. Which of the following is a common use of JSON in web development?

A) Storing and exchanging data between client and server

B) Defining CSS styles

C) Compiling JavaScript code

D) Rendering HTML elements

21 / 30

21. How can you validate JSON in a secure and efficient way?

A) Ignore validation for trusted sources

B) Manually check the JSON

C) Use a JSON Schema validator

D) Use custom regular expressions

22 / 30

22. How do you validate that a JSON object has no additional fields?

A) additionalProperties: false

B) properties: []

C) maxProperties: 0

D) additionalFields: false

23 / 30

23. What is the purpose of the space parameter in JSON.stringify()?

A) To compress the JSON output

B) To add a specific number of spaces to the start of the output

C) To format the output with indentation

D) To add extra spacing between keys and values

24 / 30

24. What does a JSON compressor do?

A) Validates JSON

B) Beautifies JSON

C) Converts JSON to XML

D) Removes unnecessary whitespace for smaller size

25 / 30

25. Which of the following tools can debug REST API calls and their JSON responses?

A) Notepad++

B) JSONLint

C) Visual Studio Code

D) Postman

26 / 30

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

A) Both key-value pairs are stored

B) The first key-value pair is ignored

C) An error is thrown

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

27 / 30

27. Which of the following JSON values is equivalent to "no value"?

A) ""

B) null

C) undefined

D) none

28 / 30

28. Which tool can be used to measure JSON parsing performance in JavaScript?

A) JSONLint

B) JSON Schema Validator

C) JSON Formatter

D) Chrome DevTools

29 / 30

29. Which extension helps debug JSON in Visual Studio Code?

A) REST Client

B) JSON Tools

C) Prettier

D) JSON Formatter

30 / 30

30. Which of the following best describes JSON?

A) A programming language

B) A lightweight data format

C) A database system

D) A markup language like XML

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