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

A) properties

B) type

C) format

D) items

2 / 30

2. What does the JSON.parse() method do in JavaScript?

A) Parses a JSON string into an XML object

B) Converts a JavaScript object into a JSON string

C) Converts a JSON string into a JavaScript object

D) Validates a JSON string

3 / 30

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

A) Deeply nested objects

B) Objects with arrays

C) Flat, simple key-value pairs

D) JSON with comments

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4. How does JSON web encryption (JWE) enhance JSON security?

A) It adds authentication to JSON

B) It compresses JSON data

C) It encrypts JSON payloads for secure transmission

D) It converts JSON to binary format

5 / 30

5. Which of the following best describes JSON?

A) A markup language like XML

B) A programming language

C) A database system

D) A lightweight data format

6 / 30

6. 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

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7. How can you debug a failing JSON API request in a browser?

A) All of the above

B) Use console.log for JSON output

C) Check the network tab in developer tools

D) Validate the response JSON using a linter

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8. Can JSON values be functions?

A) Only in arrays

B) Only in objects

C) Yes

D) No

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

A) "null"

B) (null)

C) NULL

D) null

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10. What does the Content-Security-Policy header do for JSON responses?

A) Ensures JSON is minified

B) Defines the format of JSON data

C) Specifies how JSON is cached

D) Restricts where JSON can be loaded from to prevent cross-site scripting (XSS) attacks

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11. Which of the following status codes indicates a successful API request?

A) 500

B) 403

C) 200

D) 404

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12. Which of these is a valid boolean value in JSON?

A) true

B) True

C) "true"

D) TRUE

13 / 30

13. Which of these is NOT a valid JSON value?

A) A function

B) A boolean

C) A null value

D) A string

14 / 30

14. What will JSON.stringify({ key: undefined }) return?

A) {}

B) Throws an error

C) {"key": "undefined"}

D) {"key": null}

15 / 30

15. Which of the following JSON strings can be parsed without error?

A) '{"name": "John", "age": 30}'

B) '{name: John, age: 30}'

C) '{"name": John, "age": 30}'

D) '{name: "John", age: 30}'

16 / 30

16. What is the output of the code: JSON.stringify({ key: undefined, key2: "value" });

A) {"key": "", "key2": "value"}

B) {"key": undefined, "key2": "value"}

C) {"key2": "value"}

D) {"key": null, "key2": "value"}

17 / 30

17. What is the advantage of using JSON in IoT (Internet of Things) devices?

A) It encrypts all data automatically

B) It is faster than wireless communication

C) It reduces power consumption

D) It provides a lightweight and flexible data format

18 / 30

18. What symbol is used to enclose a JSON array?

A) ()

B) {}

C) []

D) <>

19 / 30

19. Which browser's developer tools are commonly used to debug JSON in web applications?

A) Internet Explorer

B) Google Chrome

C) Safari

D) Firefox

20 / 30

20. Which database natively supports JSON as its data format?

A) SQLite

B) PostgreSQL

C) MongoDB

D) MySQL

21 / 30

21. Which of the following data types can JSON arrays contain?

A) Only strings

B) Only objects

C) Mixed data types

D) Only numbers

22 / 30

22. Which of the following is a valid JSON array?

A) <1, 2, 3>

B) (1, 2, 3)

C) {[1, 2, 3]}

D) [1, 2, 3]

23 / 30

23. How do you access the name of the first employee in the JSON structure { "department": { "employees": [ { "name": "John" }, { "name": "Alice" } ] } }?

A) department[employees][name]

B) employees[0].name

C) department.employees[1].name

D) department.employees[0].name

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. How do you handle very large JSON data efficiently in JavaScript?

A) Split the JSON file into multiple smaller files

B) Use streaming parsers like JSONStream

C) Load the entire JSON object in memory

D) Both B and C

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26. How does Elasticsearch use JSON?

A) To store and query documents

B) To render dashboards

C) To validate user input

D) To define relational tables

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27. What is the potential issue with using eval() to parse JSON strings in JavaScript?

A) Increased memory usage

B) Slower parsing

C) Vulnerability to code injection attacks

D) It cannot parse valid JSON strings

28 / 30

28. How are negative numbers represented in JSON?

A) negative123

B) -123

C) [123]

D) (123)

29 / 30

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

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

B) Convert JSON to XML

C) Minify the JSON data

D) Use large nested objects

30 / 30

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

A) Throws an error

B) {"key1": "value1"}

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

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

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