Loading... Login Loading... Register

CSS Performance Optimization Quiz

Want to learn more than this quiz offers you? Have a look at my Frontend web development courses.

Create an account and save your quiz results

Login and save your results

First Name *

Last Name *

Email *

Password *

Confirm Password *

I agree to the Terms of Service & Privacy Policy.

Add me to your newsletter.

Question 1/15

Which of these events would likely be most impacted by poor CSS performance?

Select your answer

Initial load time.

Scroll performance.

Click event responsiveness.

Page unload time.

Question 2/15

How does removing unused CSS media queries contribute to performance improvement in web applications?

Select your answer

It reduces file size, leading to faster download times and less parsing by the browser.

It frees up thread processing used for CSSOM generation.

It decreases render time during dynamic viewport changes.

It solidifies CSS specificity rules.

Question 3/15

What optimization benefit does using font-display: swap; provide for web fonts in CSS?

Select your answer

It guarantees fonts will load faster than any other setting.

It ensures fonts are always visible even if there is a delay in loading.

It reduces overall CSS file size.

It disables custom font usage entirely.

Question 4/15

How does critical CSS enhance the user experience specifically for performance?

Select your answer

It ensures all CSS is cached for subsequent page loads, improving speed.

It organizes the CSS into logical pieces reducing parse time.

It inlines the styles needed for the initial viewport, decreasing time-to-first-render and initial page load times.

It forces browsers to render pages without any styling initially.

Question 5/15

Which CSS feature, if used incorrectly, can lead to unnecessary repaints and reflows, negatively impacting performance?

Select your answer

flex

float

position: absolute

@font-face

Question 6/15

What is a potential downside of using CSS custom properties ( var(--my-variable-name) ) on very high-dynamic elements for performance?

Select your answer

They can only be used for colors.

The dynamic nature requires recalculations that could lead to performance bottlenecks if used excessively.

They are not yet supported in all browsers.

They do not work with JavaScript CSSOM.

Question 7/15

Which CSS property commonly causes reflow and should be used with caution for better performance?

Select your answer

transform

opacity

width

background-color

Question 8/15

Which of the following scenarios can result in a repaint of the document in browser rendering?

Select your answer

Changing the text color using

color

property.

Changing the font family used by an element.

Switching element visibility with

opacity

Animating the position using CSS

transform

Question 9/15

Why should you avoid using

selectors in performance-critical CSS?

Select your answer

They increase CSS specificity unnecessarily.

Browsers have slower support for these selectors.

They only work in older browsers.

They target every DOM element, causing all elements to be reconsidered during style recalculations.

Question 10/15

How does using CSS pre-processing tools like SASS or LESS improve CSS performance?

Select your answer

They inherently make styles render faster.

They utilize server-side caching automatically.

They help organize and manage styles, reducing redundancy and file size before delivery.

They enable client-side preprocessing.

Question 11/15

Why is it advisable to use only @supports rules for checking variable CSS features?

Select your answer

Directly keeps the CSSOM size smaller.

It's required for all new CSS standards.

Keeps the code cleaner and reduces the risk of applying unsupported CSS, improving performance stability.

Ensures the CSS is compatible across all browsers by default.

Question 12/15

What technique prevents layout recalculations when adding a large number of CSS-modified elements to the DOM?

Select your answer

Applying

display: none

before adding and then updating styles.

Using document fragments to insert elements in bulk.

Loading CSS styles inline instead of with external resources.

Adding each element individually with a delay.

Question 13/15

What is a key downside of placing too much CSS inline in HTML for performance purposes?

Select your answer

Increased specificity can cause issues when overriding styles.

It improves first-page rendering at the cost of subsequent loads.

Higher download time due to more HTTP requests.

Inline CSS prevents caching of styles across document requests.

Question 14/15

How can you optimize CSS animations for better performance in modern browsers?

Select your answer

Reduce the use of CSS keyframes in animations.

Use hardware-accelerated properties such as

transform

and

opacity

Avoid using animations on any element.

Always use JavaScript to manage animations.

Question 15/15

Which strategy is recommended for minimizing unused CSS to improve performance?

Select your answer

Use a tool like PurgeCSS to remove unused styles.

Manually remove all styles that seem unnecessary.

Rely on CSS minification alone.

Combine all CSS files into one large file regardless of usage.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of these events would likely be most impacted by poor CSS performance?

Available answers

Initial load time.

Scroll performance.

Click event responsiveness.

Page unload time.

Poorly optimized CSS can severely impact scroll performance as the browser might need to recalculate styles or layouts, leading to janky or sluggish scrolling behavior.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does removing unused CSS media queries contribute to performance improvement in web applications?

Available answers

It reduces file size, leading to faster download times and less parsing by the browser.

It frees up thread processing used for CSSOM generation.

It decreases render time during dynamic viewport changes.

It solidifies CSS specificity rules.

Unused CSS media queries increase the file size and complexity without contributing to functional styling, meaning removing them leads to a smaller CSS footprint and faster parsing.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

What optimization benefit does using font-display: swap; provide for web fonts in CSS?

Available answers

It guarantees fonts will load faster than any other setting.

It ensures fonts are always visible even if there is a delay in loading.

It reduces overall CSS file size.

It disables custom font usage entirely.

The

font-display: swap;

property ensures text is displayed immediately using a fallback font until the custom font can be loaded, preventing invisible text (flash of invisible text -- FOIT).

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does critical CSS enhance the user experience specifically for performance?

Available answers

It ensures all CSS is cached for subsequent page loads, improving speed.

It organizes the CSS into logical pieces reducing parse time.

It inlines the styles needed for the initial viewport, decreasing time-to-first-render and initial page load times.

It forces browsers to render pages without any styling initially.

Critical CSS involves inlining the necessary CSS for the content above the fold into the HTML to ensure it renders immediately, without waiting for external resources to load, improving user-perceived load times.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which CSS feature, if used incorrectly, can lead to unnecessary repaints and reflows, negatively impacting performance?

Available answers

<pre><code>float</code></pre>

<pre><code>position: absolute</code></pre>

When

position: absolute

is used incorrectly or excessively, it can increase the complexity of calculating the element's position, potentially leading to costly reflows.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a potential downside of using CSS custom properties ( var(--my-variable-name) ) on very high-dynamic elements for performance?

Available answers

They can only be used for colors.

The dynamic nature requires recalculations that could lead to performance bottlenecks if used excessively.

They are not yet supported in all browsers.

They do not work with JavaScript CSSOM.

CSS custom properties are resolved at runtime, meaning changes to them can cause recalculation that, if not managed carefully, can impact performance when applied to many dynamic elements.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which CSS property commonly causes reflow and should be used with caution for better performance?

Available answers

<pre><code>transform</code></pre>

<pre><code>opacity</code></pre>

<pre><code>width</code></pre>

<pre><code>background-color</code></pre>

The

width

property often causes reflow because changing the width can affect the layout of the document, meaning other elements may have to be repositioned.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following scenarios can result in a repaint of the document in browser rendering?

Available answers

Changing the text color using <pre><code>color</code></pre> property.

Changing the font family used by an element.

Switching element visibility with <pre><code>opacity</code></pre>.

Animating the position using CSS <pre><code>transform</code></pre>.

Changing the text color using the

color

property causes a repaint, as it updates how the pixels of an element are displayed visually, even though it doesn't alter its position or trigger a reflow.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why should you avoid using <pre><code>*</code></pre> selectors in performance-critical CSS?

Available answers

They increase CSS specificity unnecessarily.

Browsers have slower support for these selectors.

They only work in older browsers.

They target every DOM element, causing all elements to be reconsidered during style recalculations.

Using the universal selector

forces the browser to consider all DOM elements, leading to slower style recalculations, hence decreasing performance.

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does using CSS pre-processing tools like SASS or LESS improve CSS performance?

Available answers

They inherently make styles render faster.

They utilize server-side caching automatically.

They help organize and manage styles, reducing redundancy and file size before delivery.

They enable client-side preprocessing.

CSS preprocessors like SASS and LESS allow for variable use, nesting, and includes that can reduce redundant CSS, leading to smaller file sizes before they reach the client.

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why is it advisable to use only @supports rules for checking variable CSS features?

Available answers

Directly keeps the CSSOM size smaller.

It's required for all new CSS standards.

Keeps the code cleaner and reduces the risk of applying unsupported CSS, improving performance stability.

Ensures the CSS is compatible across all browsers by default.

@supports

rules allow conditional application of CSS depending on browser support for certain features, helping prevent unsupported rules from processing, making CSS more stable and performant.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

What technique prevents layout recalculations when adding a large number of CSS-modified elements to the DOM?

Available answers

Applying <pre><code>display: none</code></pre> before adding and then updating styles.

Using document fragments to insert elements in bulk.

Loading CSS styles inline instead of with external resources.

Adding each element individually with a delay.

Document fragments allow for elements to be inserted into the DOM in bulk, reducing the number of reflows and layout recalculations needed, thus providing better performance.

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a key downside of placing too much CSS inline in HTML for performance purposes?

Available answers

Increased specificity can cause issues when overriding styles.

It improves first-page rendering at the cost of subsequent loads.

Higher download time due to more HTTP requests.

Inline CSS prevents caching of styles across document requests.

While inline CSS can improve the initial page load, it prevents styles from being cached across requests, leading to longer load times for subsequent page views.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you optimize CSS animations for better performance in modern browsers?

Available answers

Reduce the use of CSS keyframes in animations.

Use hardware-accelerated properties such as <pre><code>transform</code></pre> and <pre><code>opacity</code></pre>.

Avoid using animations on any element.

Always use JavaScript to manage animations.

Using properties like

transform

and

opacity

leverages GPU acceleration, improving animation performance compared to other properties that may trigger reflows or repaints.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which strategy is recommended for minimizing unused CSS to improve performance?

Available answers

Use a tool like PurgeCSS to remove unused styles.

Manually remove all styles that seem unnecessary.

Rely on CSS minification alone.

Combine all CSS files into one large file regardless of usage.

Tools like PurgeCSS analyze your HTML, JavaScript, and CSS to determine which styles are used and which can be safely removed, reducing the file size and improving load times.