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 happens if a key in a JSON object contains special characters?

A) It throws an error

B) The key must be enclosed in double quotes

C) The special characters are escaped automatically

D) The key is ignored

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2. Which JavaScript function converts JSON data into a format suitable for POST requests?

A) JSON.encode()

B) JSON.parse()

C) JSON.stringify()

D) JSON.compress()

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

A) type

B) items

C) definitions

D) properties

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4. Which of the following tools allows real-time collaboration on JSON data?

A) JSON Editor Online

B) JSONLint

C) JIRA

D) Google Docs

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

A) It is faster than wireless communication

B) It provides a lightweight and flexible data format

C) It reduces power consumption

D) It encrypts all data automatically

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7. What happens when you use JSON.stringify() on an object with a circular reference?

A) It ignores the circular reference

B) It throws a TypeError

C) It throws a syntax error

D) It converts the object to a string successfully

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

A) They cannot be negative

B) They must be enclosed in double quotes

C) They support both integers and floats

D) They must include a decimal point

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

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

B) {"key2": "value"}

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

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

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10. Which of the following formats can JSON be easily converted into for data visualization?

A) HTML

B) All of the above

C) XML

D) CSV

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11. Why is it important to remove unused fields from JSON responses?

A) To reduce payload size and improve performance

B) To avoid key duplication

C) To prevent JSON schema validation errors

D) To enhance JSON readability

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

A) Converts an object to a string with formatting options

B) Converts JSON to XML

C) Compresses JSON output

D) Beautifies JSON output

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13. How does Elasticsearch use JSON?

A) To define relational tables

B) To store and query documents

C) To validate user input

D) To render dashboards

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14. Which of the following is the correct JSON format for a key-value pair?

A) {key: value}

B) {key = value}

C) {"key": "value"}

D) {"key": value}

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15. Which of the following is NOT a valid JSON key?

A) "_name"

B) name

C) "name!"

D) "123name"

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

A) settings.json

B) config.xml

C) preferences.ini

D) config.txt

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

A) none

B) undefined

C) null

D) ""

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

A) Numbers

B) Strings

C) Boolean values

D) Comments

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19. Which of these is NOT true about JSON?

A) JSON keys must always be strings

B) JSON is commonly used for APIs

C) JSON is lightweight and language-independent

D) JSON supports single-line and multi-line comments

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20. What error does a missing comma between JSON key-value pairs produce?

A) SyntaxError: Unexpected token

B) Missing property name

C) Undefined object

D) Invalid JSON

21 / 30

21. What is the MIME type for JSON?

A) text/plain

B) application/json

C) text/json

D) application/javascript

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

A) Removing all keys from JSON

B) Using only numeric data

C) Input validation and sanitization

D) Minification

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23. How do you access the value "Alice" from the JSON object {"name": "Alice", "age": 25}?

A) object["Alice"]

B) object[1]

C) object[0]

D) object.name

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24. Which of the following best describes JSON?

A) A lightweight data format

B) A programming language

C) A markup language like XML

D) A database system

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25. Can JSON values be functions?

A) Only in objects

B) No

C) Only in arrays

D) Yes

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

A) Convert JSON to XML

B) Use large nested objects

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

D) Minify the JSON data

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27. Can a JSON object be empty?

A) No

B) Yes

C) Only when nested

D) Only in arrays

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

A) Static analysis tools or manual comparison

B) JSONLint

C) JSON Formatter

D) Postman

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29. What happens if you call JSON.stringify() on a Date object?

A) Throws an error

B) The date is serialized as a timestamp

C) The date is converted to a string in ISO format

D) The date is ignored

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30. What is the effect of caching JSON responses?

A) Reduces server processing time for repeated requests

B) Converts JSON to binary format

C) Increases JSON size

D) Prevents JSON injection attacks

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