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

A) minProperties: 1

B) minItems: 1

C) minKeys: 1

D) required: true

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2. How can you format JSON output with spaces using JSON.stringify()?

A) Use the JSON.stringify(obj, null, 4) method

B) Add a spaces property to the JSON object

C) Pass a null parameter to JSON.stringify()

D) Use JSON.prettyPrint()

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

A) The format of the data being sent or expected

B) The HTTP method to be used

C) The size of the request body

D) The status of the response

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4. Which of these is NOT true about JSON?

A) JSON keys must always be strings

B) JSON is lightweight and language-independent

C) JSON is commonly used for APIs

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

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

A) department.employees[1].name

B) department[employees][name]

C) department.employees[0].name

D) employees[0].name

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6. 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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7. Which of these is a valid JSON string?

A) "Hello, World!"

B) (Hello, World!)

C) Hello, World!

D) 'Hello, World!'

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8. What does JSON stand for?

A) JavaScript Object Notation

B) Java Syntax Object Notation

C) JavaScript Online Network

D) Java Online Syntax Network

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9. How does Firebase use JSON?

A) To render user interfaces

B) To define cloud functions

C) To manage authentication tokens

D) For real-time database storage and synchronization

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

A) SQLite

B) PostgreSQL

C) MongoDB

D) MySQL

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11. What is the purpose of JSON in REST APIs?

A) To render HTML pages

B) To define API endpoints

C) To structure and exchange data between client and server

D) To validate API responses

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

A) Use JSON.stringify()

B) Avoid logging altogether

C) Log the raw JSON data as is

D) Use a secure logging framework and mask sensitive data

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13. Which tool can be used to measure JSON parsing performance in JavaScript?

A) Chrome DevTools

B) JSONLint

C) JSON Schema Validator

D) JSON Formatter

14 / 30

14. Can JSON values be arrays?

A) Only for strings

B) Yes

C) No

D) Only in objects

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

A) 404

B) 403

C) 500

D) 200

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

A) Using nested structures

B) Removing whitespace from JSON

C) Beautifying the JSON

D) Hashing the JSON content

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17. 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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18. Which of these techniques can prevent excessive JSON data exposure in APIs?

A) Compressing JSON

B) Using JSON.stringify()

C) Enabling strict validation in APIs

D) Avoiding nested JSON structures

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

A) It compresses JSON data

B) It converts JSON to binary format

C) It adds authentication to JSON

D) It encrypts JSON payloads for secure transmission

20 / 30

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

A) Prettier

B) JSON Tools

C) JSON Formatter

D) REST Client

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21. What is the output of JSON.stringify() on a nested object?

A) A deep copy of the object

B) A string representation of the nested object

C) A flattened version of the object

D) Throws an error

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22. Can JSON objects be nested inside other JSON objects?

A) Only with arrays

B) No

C) Yes

D) Only with strings

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23. What is JSON primarily used for?

A) Data exchange between a client and a server

B) Creating animations

C) Styling web pages

D) Sending emails

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

A) Use JSON.check()

B) Use JSON.isValid()

C) Use typeof to check its type

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

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25. 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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26. JSON is _______________.

A) None of the above

B) Case-insensitive

C) Case-sensitive

D) Partially case-sensitive

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

A) undefined

B) null

C) "Hello"

D) 123

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

A) Use a JSON Schema validator

B) Manually check the JSON

C) Ignore validation for trusted sources

D) Use custom regular expressions

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29. 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()

30 / 30

30. Which JavaScript method can convert an object into a JSON string for an API request?

A) JSON.parse()

B) JSON.encode()

C) JSON.stringify()

D) JSON.serialize()

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