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 online tool is commonly used to format JSON for readability?

A) Postman

B) JSONLint

C) GitHub

D) Visual Studio Code

2 / 30

2. 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

3 / 30

3. How do you validate that a JSON object has no additional fields?

A) additionalFields: false

B) maxProperties: 0

C) additionalProperties: false

D) properties: []

4 / 30

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

A) Firefox

B) Safari

C) Google Chrome

D) Internet Explorer

5 / 30

5. What is the purpose of an API key in requests?

A) To specify the API version

B) To indicate the request priority

C) To authenticate the client

D) To encrypt the request data

6 / 30

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

A) Throws an error

B) {"key": null}

C) {"key": "undefined"}

D) {}

7 / 30

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

A) Postman and JMeter

B) Jenkins and Kubernetes

C) Figma and Sketch

D) Selenium and Puppeteer

8 / 30

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

A) Hyphen

B) Comma

C) Semicolon

D) Colon

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

A) Use key.parent

B) Use parent() function

C) JSON does not support parent references

D) Use a library to navigate JSON paths

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

A) Throws a SyntaxError

B) Skips invalid parts

C) Returns null

D) Converts to an empty object

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11. What does the oneOf keyword do in JSON Schema?

A) Requires all listed schemas to match

B) Validates against one specific type

C) Ensures that the data matches exactly one of the specified schemas

D) Combines multiple schemas

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

A) To enhance JSON readability

B) To prevent JSON schema validation errors

C) To avoid key duplication

D) To reduce payload size and improve performance

13 / 30

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

A) Increased memory usage

B) Vulnerability to code injection attacks

C) It cannot parse valid JSON strings

D) Slower parsing

14 / 30

14. Which of the following is a valid JSON string?

A) "Hello"

B) “Hello”

C) Hello

D) 'Hello'

15 / 30

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

A) undefined

B) null

C) "Hello"

D) 123

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16. What is the purpose of using JSON Web Tokens (JWT)?

A) To convert JSON into binary format

B) To beautify JSON

C) To replace JSON

D) To validate and secure data transmission

17 / 30

17. Can JSON values be arrays?

A) Only for strings

B) Yes

C) Only in objects

D) No

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

A) maxItems

B) minLength

C) arrayLimit

D) maxSize

19 / 30

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

A) A key-value pair object

B) ReferenceError

C) null

D) SyntaxError: Unexpected identifier

20 / 30

20. Which of the following is NOT a JSON data type?

A) Date

B) Null

C) String

D) Boolean

21 / 30

21. JSON is a strict subset of which language?

A) SQL

B) Python

C) XML

D) JavaScript

22 / 30

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

A) JSON Formatter

B) JSONLint

C) jq

D) Postman

23 / 30

23. Which of the following is the correct way to represent an empty JSON object?

A) null

B) ""

C) {}

D) []

24 / 30

24. 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

25 / 30

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

A) Both B and C

B) Load the entire JSON object in memory

C) Use streaming parsers like JSONStream

D) Split the JSON file into multiple smaller files

26 / 30

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

A) name

B) "123name"

C) "name!"

D) "_name"

27 / 30

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

A) Avoid logging altogether

B) Log the raw JSON data as is

C) Use a secure logging framework and mask sensitive data

D) Use JSON.stringify()

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28. 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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29. What can be the root structure of a JSON document?

A) Either an object or an array

B) A string

C) Only an array

D) Only an object

30 / 30

30. Which JSON data type is used to group key-value pairs?

A) Object

B) Array

C) String

D) Number

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