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.

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

A) To format the output with indentation

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

C) To add extra spacing between keys and values

D) To compress the JSON output

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

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

B) {"key1": "value1"}

C) Throws an error

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

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3. What does a JSON path debugger do?

A) Extracts specific values from JSON

B) Validates JSON syntax

C) Beautifies JSON

D) Converts JSON to CSV

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

A) It converts JSON to binary format

B) It compresses JSON data

C) It encrypts JSON payloads for secure transmission

D) It adds authentication to JSON

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5. How do you check if a string is valid JSON in JavaScript?

A) Parse it with JSON.parse() inside a try...catch block

B) Use typeof to check its type

C) Use JSON.isValid()

D) Use JSON.check()

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

A) A function

B) A null value

C) A string

D) A boolean

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

A) They support both integers and floats

B) They cannot be negative

C) They must be enclosed in double quotes

D) They must include a decimal point

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8. How do you specify a format for email validation in JSON Schema?

A) type: "email"

B) format: "email"

C) validate: "email"

D) pattern: "/[email]/"

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

A) The data format expected in the response

B) The server's API version

C) The client type

D) The authentication type

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

A) Use key.parent

B) Use parent() function

C) Use a library to navigate JSON paths

D) JSON does not support parent references

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11. What happens if a key in a JSON object contains special characters?

A) The key is ignored

B) It throws an error

C) The key must be enclosed in double quotes

D) The special characters are escaped automatically

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12. In which cloud service is JSON commonly used for defining infrastructure as code?

A) Firebase

B) DigitalOcean

C) Amazon Web Services (AWS) CloudFormation

D) Microsoft Azure

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13. 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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14. Can JSON keys have spaces?

A) Yes, with quotes

B) Only in arrays

C) No

D) Yes, without quotes

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15. What happens when you use JSON.parse() on an invalid JSON string?

A) Returns null

B) Skips invalid parts

C) Throws a SyntaxError

D) Converts to an empty object

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16. 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>

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17. What is one method to detect changes in JSON data?

A) Using nested structures

B) Removing whitespace from JSON

C) Hashing the JSON content

D) Beautifying the JSON

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

A) Number

B) String

C) Boolean

D) Undefined

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19. JSON is a strict subset of which language?

A) XML

B) Python

C) SQL

D) JavaScript

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20. 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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21. Which keyword restricts the number of items in a JSON array?

A) maxSize

B) maxItems

C) arrayLimit

D) minLength

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22. What is the output of JSON.stringify([1, undefined, 2])?

A) Throws a TypeError

B) "[1, undefined, 2]"

C) "[1, null, 2]"

D) "[1, , 2]"

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23. Which messaging protocol often uses JSON for message payloads?

A) POP3

B) SMTP

C) FTP

D) MQTT

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

A) Use custom regular expressions

B) Ignore validation for trusted sources

C) Use a JSON Schema validator

D) Manually check the JSON

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25. What is JSON Schema?

A) A specification to define and validate the structure of JSON data

B) A library to parse JSON data

C) A method to minify JSON files

D) A format to store JSON data

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26. What does a JSON Formatter do?

A) Compresses JSON into a single line

B) Parses JSON into JavaScript objects

C) Formats JSON into a readable and indented structure

D) Converts JSON to XML

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27. Can JSON values be functions?

A) Only in arrays

B) Yes

C) No

D) Only in objects

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28. How can large nested JSON objects impact performance?

A) They make JSON more secure

B) They improve network speed

C) They slow down parsing and increase memory usage

D) They reduce API latency

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

A) Postman

B) Visual Studio Code

C) Notepad++

D) JSONLint

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30. What is JSON primarily used for?

A) Styling web pages

B) Creating animations

C) Data exchange between a client and a server

D) Sending emails

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