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 testing tools commonly use JSON for request and response data?

A) Selenium and Puppeteer

B) Jenkins and Kubernetes

C) Postman and JMeter

D) Figma and Sketch

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2. What is the primary role of JSON in GraphQL APIs?

A) To handle authentication

B) To define the schema

C) To format query results

D) To manage subscriptions

3 / 30

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

A) "name!"

B) "_name"

C) "123name"

D) name

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4. Which of the following values can be used as JSON keys?

A) Strings only

B) Any data type

C) Strings and numbers

D) Strings and booleans

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5. What does the enum keyword specify in JSON Schema?

A) A list of allowed values for a property

B) The maximum length of a string

C) The default value of a property

D) The format of a date field

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6. What is a safe alternative to eval() for parsing JSON in JavaScript?

A) JSON.debug()

B) JSON.minify()

C) JSON.parse()

D) JSON.stringify()

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7. Which HTTP header is critical for securing JSON responses?

A) Accept-Encoding

B) X-Content-Type-Options

C) Access-Control-Allow-Origin

D) Content-Type

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

A) Use JSON.check()

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

C) Use typeof to check its type

D) Use JSON.isValid()

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9. JSON is _______________.

A) Case-insensitive

B) Partially case-sensitive

C) None of the above

D) Case-sensitive

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10. Which of the following is a commonly used library for making API requests in JavaScript?

A) Lodash

B) Axios

C) D3.js

D) jQuery

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11. JSON is a strict subset of which language?

A) XML

B) Python

C) JavaScript

D) SQL

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

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

B) Validates against one specific type

C) Combines multiple schemas

D) Requires all listed schemas to match

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

A) It throws a TypeError

B) It ignores the circular reference

C) It throws a syntax error

D) It converts the object to a string successfully

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14. 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

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15. What is the default value of additionalProperties in JSON Schema?

A) true

B) false

C) null

D) undefined

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16. Which online tool is commonly used to format JSON for readability?

A) GitHub

B) JSONLint

C) Postman

D) Visual Studio Code

17 / 30

17. What happens if there is a syntax error in a JSON file?

A) It will fail to parse

B) The JSON file still works

C) It displays a warning but continues

D) It gets ignored

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

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

B) Use JSON.prettyPrint()

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

D) Add a spaces property to the JSON object

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19. How is JSON used in data interchange for machine learning models?

A) To train models directly

B) To compile machine learning libraries

C) To render visualizations

D) To serialize model configurations and results

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

A) JSON Formatter

B) jq

C) JSONLint

D) Postman

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21. Which of the following is used to validate the syntax of JSON data?

A) JSON Compressor

B) JSON Validator

C) JSON Beautifier

D) JSON Formatter

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

A) The key must be enclosed in double quotes

B) The key is ignored

C) The special characters are escaped automatically

D) It throws an error

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23. How can you handle errors when parsing JSON in JavaScript?

A) Checking the JSON string with isValid()

B) Using the JSON.validate() method

C) JSON parsing cannot produce errors

D) Using a try...catch block

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

A) Hello

B) “Hello”

C) "Hello"

D) 'Hello'

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25. Why should you limit the depth of nested JSON objects?

A) To reduce data size

B) To remove duplicate keys

C) To prevent DoS attacks caused by deep recursion

D) To improve readability

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26. Which of these is NOT true about JSON?

A) JSON is lightweight and language-independent

B) JSON keys must always be strings

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

D) JSON is commonly used for APIs

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

A) settings.json

B) config.xml

C) config.txt

D) preferences.ini

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28. Which method can be used to transform a JSON object into an iterable array?

A) Object.keys()

B) Object.values()

C) Object.entries()

D) All of the above

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29. What is the result of JSON.parse('null') in JavaScript?

A) Converts to the string "null"

B) Returns null

C) Throws a syntax error

D) Returns undefined

30 / 30

30. How do you represent a null value in JSON?

A) "null"

B) NULL

C) null

D) (null)

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