What is The difference between Em and rem? All Important Interview Question At the Bottom Of the Blog check it out.
Understanding em and rem in CSS #css #interviewquestions
When you're learning CSS, you'll come across different units that are used for specifying sizes, like pixels, percentages, ems and rems. Two units that can be confusing are em and rem. In this blog, I'll explain what they are and how they work in an easy to understand way.
Pixels vs Relative Units
Pixels (px) are fixed units - they always represent the same size. For example, 16px will always be 16 pixels.
But em and rem are relative units - their size depends on something else. This makes them really useful in CSS!
What is em?
1em = the font size of the parent element. Easy!
For Example:
<html>
<head>
<style>
body {
font-size: 16px;
}
p {
font-size: 1em; /* 16px */
}
.special {
font-size: 2em; /* 32px */
}
</style>
</head>
<body>
<p>This paragraph text will be 16px.</p>
<p class="special">This paragraph text will be 32px.</p>
</body>
</html>
html {
font-size: 16px;
}
p {
font-size: 1rem; /* Equal to 16px */
}
.special {
font-size: 2rem; /* Equal to 32px (2 * 16px) */
}
What is rem?
The rem unit is similar to em, but it's relative to the root html element's font size.
html {
font-size: 16px;
}
p {
font-size: 1rem; /* Equal to 16px */
}
.special {
font-size: 2rem; /* Equal to 32px (2 * 16px) */
}
Now the html base size is 16px. When we set paragraph text to 1rem, it equals 16px. And 2rem equals 32px.
So 1rem = the html font size. Rem is relative to the root, not the parent.
When to use em vs rem?
Use em for font sizes when you want them to scale relative to a parent element. This is common in media queries to adjust sizes for different devices.
Use rem for font sizes when you want a consistent size relative to the html. This avoids cascading size changes when nested.
I hope this helps explain the difference between em and rem! Let me know if you have any other questions.
<html>
<head>
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<style>
body {
font-size: 16px;
}
p {
font-size: 1em; /* 16px */
}
.special {
font-size: 2em; /* 32px */
}
</style>
</head>
<body>
<p>This paragraph text will be 16px.</p>
<p class="special">This paragraph text will be 32px.</p>
</body>
</html>
In this example:
- The body font-size is set to 16px.
- The p tag font-size is set to 1em, which equals the body size of 16px.
- The .special paragraph class sets font-size to 2em.
- Since 1em = 16px (the body size), 2em = 32px.
So the em unit allows the .special paragraph text to be scaled relative to its parent body element font-size. This shows how em can be useful for responsively sizing elements.
Let me know if you need any clarification or have additional questions!
Here are some potential interview questions related to em and rem in CSS:
1. What is the difference between em and rem units in CSS?
- Em is relative to the font size of the parent element, rem is relative to the html root font size. Em can cause nested font sizes to compound, rem provides more consistency.
2. When is it better to use em over rem?
- Use em for font sizes when you need them to scale relative to a parent container, like within media queries to adjust font size responsively across screen sizes.
3. What are the benefits of using rem for font sizes?
- Rem creates consistency in font sizes, avoids cascading changes when nested, and prevents compounding size changes across descendants.
4. How would you size a paragraph to be twice as big as the body font size using em?
- Set the body font-size to 16px, then set the paragraph font-size to 2em. Since 1em = 16px, 2em will equal 32px.
5. How can using only pixel font sizes be problematic for responsive design?
- Pixel sizes are fixed and don't adapt to different viewport sizes. Using relative units like em or rem allows font sizes to scale relatively for responsive design.
6. How would you scale an entire website's font size up for accessibility?
- Set the html font-size to a larger value like 20px. Then use rem units for font sizes. This will scale all rem units up proportionally.
So I hope You guys get some value from this if you have any question than you can ask me in comments i will definitely reply to all of you guys. Thank you
Founder Codeoptics..........