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 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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2. What does a JSON compressor do?

A) Beautifies JSON

B) Validates JSON

C) Converts JSON to XML

D) Removes unnecessary whitespace for smaller size

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3. Which keyword defines a numeric range in JSON Schema?

A) min and max

B) range

C) minimum and maximum

D) numberRange

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

A) "null"

B) (null)

C) NULL

D) null

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

A) JSON Formatter

B) REST Client

C) JSON Tools

D) Prettier

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

A) Converts an object to a string with formatting options

B) Beautifies JSON output

C) Compresses JSON output

D) Converts JSON to XML

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

A) object[0]

B) object["Alice"]

C) object[1]

D) object.name

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8. What is the purpose of application/json MIME type?

A) To parse JSON

B) To convert JSON to XML

C) To define JSON structure

D) To identify JSON data format

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

A) ""

B) []

C) {}

D) null

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

A) It throws an error

B) The special characters are escaped automatically

C) The key is ignored

D) The key must be enclosed in double quotes

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

A) maxProperties: 0

B) properties: []

C) additionalProperties: false

D) additionalFields: false

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

A) jQuery

B) D3.js

C) Lodash

D) Axios

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13. What is the effect of caching JSON responses?

A) Converts JSON to binary format

B) Reduces server processing time for repeated requests

C) Increases JSON size

D) Prevents JSON injection attacks

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14. Which of these is a valid boolean value in JSON?

A) True

B) TRUE

C) "true"

D) true

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15. How do you identify invalid JSON in a web application?

A) Use the browser's developer tools

B) All of the above

C) Log errors in the console

D) Use a linter or formatter tool

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16. What does the Content-Security-Policy header do for JSON responses?

A) Defines the format of JSON data

B) Specifies how JSON is cached

C) Ensures JSON is minified

D) Restricts where JSON can be loaded from to prevent cross-site scripting (XSS) attacks

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

A) Postman

B) JSONLint

C) Visual Studio Code

D) GitHub

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18. What is the root element of a JSON document?

A) A key-value pair

B) A string

C) An object or array

D) A number

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19. 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 JSON.isValid()

C) Use typeof to check its type

D) Use JSON.check()

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20. Which of the following is a valid JSON array?

A) {"1", "2", "3"}

B) [1; 2; 3]

C) [1, 2, "three"]

D) (1, 2, 3)

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21. What does the type keyword accept for mixed data types?

A) A single string

B) A numeric range

C) An array of types

D) A boolean flag

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

A) Only with strings

B) No

C) Yes

D) Only with arrays

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23. Can a JSON object be empty?

A) Yes

B) No

C) Only in arrays

D) Only when nested

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

A) Throws an error

B) A flattened version of the object

C) A string representation of the nested object

D) A deep copy of the object

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25. What is the purpose of the Authorization header in API requests?

A) To specify the API version

B) To include authentication credentials

C) To set request priority

D) To specify data format

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

A) “Hello”

B) Hello

C) "Hello"

D) 'Hello'

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27. What is the difference between allOf and oneOf in JSON Schema?

A) allOf is for strings, oneOf is for arrays

B) allOf validates all schemas, oneOf validates only one schema

C) allOf allows duplicates, oneOf does not

D) oneOf requires at least one match, allOf requires none

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28. What is the correct syntax for a JSON object?

A) [key: "value"]

B) {key = "value"}

C) {key: "value"}

D) {"key": "value"}

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29. How do you access the second element of a JSON array ["apple", "banana", "cherry"]?

A) array[1]

B) array.get(1)

C) array.index(1)

D) array["banana"]

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

A) Skips invalid parts

B) Returns null

C) Throws a SyntaxError

D) Converts to an empty object

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