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 does the title keyword do in JSON Schema?

A) Provides a description of the schema

B) Specifies a string pattern

C) Gives a short label to the schema or property

D) Sets a required field

2 / 30

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

A) To specify required properties

B) To include reusable schema definitions

C) To define a default value

D) To reference external files

3 / 30

3. 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}'

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

A) [1, 2, undefined, 4]

B) Throws a SyntaxError

C) [1, 2, , 4]

D) [1, 2, null, 4]

5 / 30

5. Which of the following is NOT a valid use case of JSON.stringify()?

A) Formatting JSON output with indentation

B) Serializing objects with circular references

C) Converting JavaScript objects into readable JSON format

D) Serializing objects for storage or transmission

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6. Which of the following is true about JSON numbers?

A) They must include a decimal point

B) They support both integers and floats

C) They must be enclosed in double quotes

D) They cannot be negative

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

A) It provides a lightweight and flexible data format

B) It encrypts all data automatically

C) It reduces power consumption

D) It is faster than wireless communication

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8. What is the result of running JSON.parse('{"key":value}') in JavaScript?

A) ReferenceError

B) A key-value pair object

C) SyntaxError: Unexpected identifier

D) null

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

A) It skips the circular reference and continues

B) It converts successfully

C) It returns an empty object

D) It throws a TypeError

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10. Which of the following is an example of a nested JSON object?

A) { "name": "John" }

B) { "person": { "name": "John", "age": 30 } }

C) [ "John", 30 ]

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

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11. How is null represented in JSON?

A) NULL

B) null

C) (null)

D) "null"

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

A) Converts JSON to XML

B) Converts an object to a string with formatting options

C) Compresses JSON output

D) Beautifies JSON output

13 / 30

13. Which method is used to convert a JavaScript object into a JSON string?

A) JSON.toString()

B) JSON.stringify()

C) JSON.parse()

D) JSON.encode()

14 / 30

14. What separates two key-value pairs in a JSON object?

A) Hyphen

B) Comma

C) Semicolon

D) Colon

15 / 30

15. Which of the following is NOT valid in JSON?

A) Comments

B) Boolean values

C) Numbers

D) Strings

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16. How can you find the length of an array inside a JSON object?

A) jsonObject.array.len

B) jsonObject.array.count()

C) jsonObject.array.length

D) jsonObject.array.size()

17 / 30

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

A) "true"

B) True

C) true

D) TRUE

18 / 30

18. 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)

19 / 30

19. Which of the following files often uses JSON for configuration?

A) settings.json

B) preferences.ini

C) config.xml

D) config.txt

20 / 30

20. Can JSON values be arrays?

A) Yes

B) Only for strings

C) Only in objects

D) No

21 / 30

21. What does the Content-Type header specify in an API request?

A) The HTTP method to be used

B) The status of the response

C) The size of the request body

D) The format of the data being sent or expected

22 / 30

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

A) Figma and Sketch

B) Jenkins and Kubernetes

C) Selenium and Puppeteer

D) Postman and JMeter

23 / 30

23. Which of these is a valid JSON string?

A) (Hello, World!)

B) "Hello, World!"

C) 'Hello, World!'

D) Hello, World!

24 / 30

24. What is the correct JSON format for a boolean value?

A) True or False

B) "true" or "false"

C) true or false

D) TRUE or FALSE

25 / 30

25. JSON is a strict subset of which language?

A) JavaScript

B) Python

C) SQL

D) XML

26 / 30

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

A) Use a secure logging framework and mask sensitive data

B) Log the raw JSON data as is

C) Use JSON.stringify()

D) Avoid logging altogether

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27. Which tool can convert a JSON file into a different format like CSV?

A) JSONLint

B) JSON Formatter

C) Postman

D) jq

28 / 30

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

A) Check the network tab in developer tools

B) Validate the response JSON using a linter

C) Use console.log for JSON output

D) All of the above

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29. How do you represent a key-value pair where the value is an array?

A) { "key": { "value1": "value2" } }

B) [ { "key": "value1" } ]

C) { "key": "value1", "value2" }

D) { "key": [ "value1", "value2" ] }

30 / 30

30. 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

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