20 Web Performance Optimization Quiz Questions and Answers

Question 1:
What is the primary purpose of minifying CSS and JavaScript files in web performance optimization?
A) To increase file size for better readability
B) To reduce file size by removing unnecessary characters
C) To add comments for debugging
D) To encrypt the code for security

Answer: B
Explanation: Minifying CSS and JavaScript files removes whitespace, comments, and other unnecessary characters, which decreases file size and speeds up download times, improving overall page load performance.

Question 2:
Which HTTP protocol version is designed to improve web performance by allowing multiple requests over a single connection?
A) HTTP/1.1
B) HTTP/2
C) HTTP/3
D) HTTP/0.9

Answer: B
Explanation: HTTP/2 introduces multiplexing, which allows multiple requests and responses to be sent over a single TCP connection, reducing latency and improving efficiency compared to HTTP/1.1.

Question 3:
What does lazy loading primarily help achieve in web pages?
A) Loading all images at once for faster initial render
B) Deferring the loading of non-essential resources until needed
C) Compressing images on the server
D) Automatically resizing images based on screen size

Answer: B
Explanation: Lazy loading delays the loading of off-screen or non-critical elements, such as images, until they are about to enter the viewport, which reduces initial page load time and saves bandwidth.

Question 4:
In web performance, what is the main benefit of using browser caching?
A) It forces users to download files every time
B) It stores resources locally so they can be reused without re-downloading
C) It increases server requests for validation
D) It disables all cookies on the site

Answer: B
Explanation: Browser caching allows static resources like images and scripts to be stored in the user’s browser cache, enabling faster subsequent page loads by avoiding repeated downloads from the server.

Question 5:
Which technique involves breaking down a large JavaScript bundle into smaller chunks for on-demand loading?
A) Code bundling
B) Code splitting
C) Minification
D) Obfuscation

Answer: B
Explanation: Code splitting divides JavaScript code into smaller bundles that can be loaded asynchronously as needed, reducing the initial load time and improving the perceived performance of the application.

Question 6:
What is the key advantage of using a Content Delivery Network (CDN) for static assets?
A) It centralizes all traffic to one server
B) It distributes content across global servers to reduce latency
C) It increases the number of HTTP requests
D) It only works for dynamic content

Answer: B
Explanation: A CDN replicates static assets across multiple servers worldwide, allowing users to access content from the nearest server, which minimizes latency and enhances load times.

Question 7:
How does image compression impact web performance?
A) It increases file sizes to preserve quality
B) It reduces file sizes without significantly losing quality, speeding up loads
C) It adds metadata to images for SEO
D) It prevents images from being cached

Answer: B
Explanation: Image compression techniques, such as lossless or lossy methods, shrink file sizes while maintaining acceptable quality, resulting in faster downloads and better overall page performance.

Question 8:
What role does the Critical Rendering Path (CRP) play in web performance?
A) It delays the rendering of all elements
B) It outlines the sequence of steps for the browser to render a page, allowing optimizations to speed it up
C) It focuses only on server-side rendering
D) It ignores CSS and JavaScript files

Answer: B
Explanation: The Critical Rendering Path is the sequence of steps the browser takes to parse and render a page, and optimizing it—by prioritizing critical resources—helps reduce the time to first paint.

Question 9:
Which metric measures the time it takes for the browser to start displaying any content on the page?
A) Time to Interactive (TTI)
B) First Input Delay (FID)
C) First Contentful Paint (FCP)
D) Largest Contentful Paint (LCP)

Answer: C
Explanation: First Contentful Paint (FCP) measures the time from navigation to when the browser renders the first piece of content, providing insight into perceived load speed.

Question 10:
What is the primary goal of reducing the number of DNS lookups in web performance?
A) To increase the total number of requests
B) To minimize the time spent resolving domain names before loading resources
C) To add more subdomains for better organization
D) To disable HTTPS entirely

Answer: B
Explanation: DNS lookups add latency as the browser resolves domain names; reducing them by consolidating resources under fewer domains speeds up the initial connection process.

Question 11:
In web performance optimization, what does enabling Gzip compression achieve?
A) It expands file sizes for easier editing
B) It compresses text-based assets like HTML, CSS, and JavaScript to reduce transfer size
C) It only affects images
D) It slows down server response times

Answer: B
Explanation: Gzip compression algorithm reduces the size of HTTP responses for text files, leading to faster transmission over the network and improved page load times.

Question 12:
Which practice helps eliminate render-blocking resources on a web page?
A) Placing all scripts in the head section
B) Using async or defer attributes for non-essential scripts
C) Loading CSS after the page content
D) Increasing the size of inline scripts

Answer: B
Explanation: The async and defer attributes allow scripts to load without blocking the HTML parsing and rendering process, enabling the page to display content faster.

Question 13:
What is the main benefit of using WebP format for images in web performance?
A) It increases image file sizes for higher resolution
B) It provides better compression and quality compared to JPEG or PNG, reducing load times
C) It is only compatible with older browsers
D) It adds animation to static images

Answer: B
Explanation: WebP offers superior lossless and lossy compression for images, resulting in smaller file sizes than traditional formats, which accelerates page loading.

Question 14:
How does implementing service workers enhance web performance?
A) By disabling caching entirely
B) By enabling offline access and caching strategies to serve content faster
C) By increasing the number of network requests
D) By limiting the use of HTTPS

Answer: B
Explanation: Service workers act as a proxy between the web app and the network, allowing for caching, background syncing, and offline functionality, which improves load times and user experience.

Question 15:
What does the Total Blocking Time (TBT) metric indicate in web performance?
A) The time spent on non-blocking tasks
B) The amount of time that main thread is blocked, preventing user input
C) The total time for all page resources to load
D) The delay in server responses

Answer: B
Explanation: Total Blocking Time measures the periods when the main thread is blocked by long tasks, which can delay interactivity and affect user perception of performance.

Question 16:
Which optimization technique involves prioritizing above-the-fold content to improve perceived speed?
A) Deferred loading
B) Critical CSS inlining
C) Full page caching
D) Image hoisting

Answer: B
Explanation: Inlining critical CSS—styles needed for above-the-fold content—allows the browser to render the initial viewport faster, enhancing the perceived loading speed.

Question 17:
What is the impact of using HTTP/2’s server push feature?
A) It pushes unnecessary data to the client
B) It allows the server to send resources to the client before they are requested, reducing round trips
C) It disables multiplexing
D) It only works with HTTP/1.1

Answer: B
Explanation: Server push in HTTP/2 proactively sends dependent resources (like CSS or JS) with the initial response, minimizing additional requests and improving load times.

Question 18:
In web performance, why is it important to optimize the render tree construction?
A) To delay the painting of elements
B) To ensure the browser builds the render tree efficiently, avoiding unnecessary recalculations
C) To increase CPU usage
D) To ignore DOM changes

Answer: B
Explanation: Optimizing render tree construction involves minimizing DOM size and avoiding layout thrashing, which speeds up the process of turning the DOM and CSSOM into rendered pixels.

Question 19:
What does the Largest Contentful Paint (LCP) metric focus on?
A) The time when the page becomes interactive
B) The render time of the largest content element visible in the viewport
C) The total number of images loaded
D) The delay in user inputs

Answer: B
Explanation: Largest Contentful Paint measures the time it takes for the largest element (like an image or block of text) to become visible, indicating how quickly the main content loads.

Question 20:
How can reducing third-party scripts improve web performance?
A) By increasing the page’s dependency on external services
B) By minimizing additional network requests and potential blocking
C) By adding more ads to the page
D) By disabling core functionality

Answer: B
Explanation: Third-party scripts often introduce extra requests and can block the main thread; reducing or optimizing them lowers latency and improves overall page speed.