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 use of the $ref keyword in JSON Schema?

A) To reference external files

B) To include reusable schema definitions

C) To define a default value

D) To specify required properties

2 / 30

2. What is the best approach to log sensitive information within JSON responses?

A) Use JSON.stringify()

B) Use a secure logging framework and mask sensitive data

C) Avoid logging altogether

D) Log the raw JSON data as is

3 / 30

3. How do you reference the parent key in a deeply nested JSON object?

A) JSON does not support parent references

B) Use a library to navigate JSON paths

C) Use parent() function

D) Use key.parent

4 / 30

4. What does the Accept header specify in an API request?

A) The authentication type

B) The client type

C) The server's API version

D) The data format expected in the response

5 / 30

5. Can JSON values be functions?

A) Yes

B) No

C) Only in arrays

D) Only in objects

6 / 30

6. Which HTTP method is commonly used to fetch JSON data from an API?

A) DELETE

B) PUT

C) GET

D) POST

7 / 30

7. Which of these is valid for a JSON number?

A) 1.23

B) All of the above

C) -456

D) 123e5

8 / 30

8. Can JSON objects contain duplicate keys?

A) No

B) Yes, but only for strings

C) Yes, with an error

D) Yes, the last key-value pair overrides the previous ones

9 / 30

9. What does a 404 status code signify in an API response?

A) Unauthorized access

B) Resource not found

C) Internal server error

D) Bad request

10 / 30

10. Which of the following values is not valid in JSON?

A) undefined

B) "Hello"

C) null

D) 123

11 / 30

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

A) Axios

B) D3.js

C) jQuery

D) Lodash

12 / 30

12. What does the properties keyword do in JSON Schema?

A) Specifies the data type of an array

B) Lists all required fields in an object

C) Defines the keys allowed in an object

D) Defines the maximum number of keys in an object

13 / 30

13. How do you represent a null value in JSON?

A) "null"

B) null

C) (null)

D) NULL

14 / 30

14. What is the primary advantage of using binary JSON formats like BSON?

A) Smaller size and faster parsing

B) Automatic validation

C) Enhanced readability

D) Compatibility with XML

15 / 30

15. What is the purpose of using JSON Web Tokens (JWT)?

A) To beautify JSON

B) To validate and secure data transmission

C) To replace JSON

D) To convert JSON into binary format

16 / 30

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

A) Load the entire JSON at once

B) Convert JSON to XML first

C) Use streaming APIs to process JSON incrementally

D) Remove all nested objects

17 / 30

17. What is the result of JSON.parse('null') in JavaScript?

A) Converts to the string "null"

B) Returns undefined

C) Returns null

D) Throws a syntax error

18 / 30

18. What will be the output of the code: JSON.stringify({ key1: "value1", key2: function() { return "value2"; } });

A) {"key1": "value1", "key2": "value2"}

B) {"key1": "value1", "key2": null}

C) {"key1": "value1"}

D) Throws an error

19 / 30

19. Which type of JSON structure is most efficient for transmitting data?

A) Flat, simple key-value pairs

B) JSON with comments

C) Deeply nested objects

D) Objects with arrays

20 / 30

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

A) minItems: 1

B) required: true

C) minProperties: 1

D) minKeys: 1

21 / 30

21. What does a JSON Formatter do?

A) Compresses JSON into a single line

B) Converts JSON to XML

C) Parses JSON into JavaScript objects

D) Formats JSON into a readable and indented structure

22 / 30

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

A) To avoid key duplication

B) To reduce client-side processing time

C) To improve network performance and reduce latency

D) To increase readability

23 / 30

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

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

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

C) allOf is for strings, oneOf is for arrays

D) allOf allows duplicates, oneOf does not

24 / 30

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

A) A string

B) Either an object or an array

C) Only an array

D) Only an object

25 / 30

25. How can you identify unused keys in a JSON object?

A) Static analysis tools or manual comparison

B) JSON Formatter

C) Postman

D) JSONLint

26 / 30

26. Which keyword is used to specify required fields in a JSON object?

A) fields

B) mandatory

C) required

D) include

27 / 30

27. Can JSON keys have spaces?

A) No

B) Only in arrays

C) Yes, with quotes

D) Yes, without quotes

28 / 30

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

A) REST Client

B) JSON Formatter

C) Prettier

D) JSON Tools

29 / 30

29. What is the correct syntax for a JSON object?

A) [key: "value"]

B) {"key": "value"}

C) {key: "value"}

D) {key = "value"}

30 / 30

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

A) Use large nested objects

B) Minify the JSON data

C) Convert JSON to XML

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

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