Designing with CSS Units for a Seamless User Experience is crucial for a responsive font size. Using relative units like em, rem, and viewport-percentage units can help achieve this.
Relative units, such as em, rem, and viewport-percentage units, are based on the size of the element or the viewport, making them ideal for responsive design. For example, using rem units can ensure that font sizes scale consistently across different devices.
The em unit is based on the font size of the parent element, while the rem unit is based on the root element, making rem a more reliable choice for responsive design. This is demonstrated in the example where a font size of 1.5rem is used, resulting in a font size of 18px on a device with a base font size of 12px.
Using relative units can also help avoid the "font size explosion" problem, where font sizes increase exponentially on larger screens. By using relative units, you can maintain a consistent font size across different devices and screen sizes.
Why Use Responsive Font Size?
Using responsive font size is crucial to make your website more usable and accessible across different screen sizes. This means you need to adapt your font size to the user's screen, whether it's a desktop or a mobile device.
If you set a static font size, it may look huge on a mobile screen or too small on a desktop. Users expect larger fonts on desktop websites and smaller fonts on mobile websites. You can use rem units to set font sizes, as they point to the root element and are relative to the font size of the root element.
To make font sizes responsive, you can use the vw unit, where 1vw equals 1% of the viewport width. This means the font size will change proportionally as the viewport width changes.
Here are some recommended use cases for CSS units:
Why Use Text?
Using responsive text is a must for making your website more usable and accessible across different screen sizes.
Your visitors may have trouble reading your text content if you don't use responsive text. For example, headings that look perfect on a desktop may be huge and distracting on a mobile screen.
Users have come to expect generally larger fonts on desktop websites and generally smaller fonts on mobile websites.
If you keep the same font size on a mobile screen, headings will look huge and potentially distract readers.
Responsive
Responsive font sizes are a game-changer for making your website more accessible and user-friendly across different screen sizes.
Using the vw unit is a great way to make font sizes responsive, where 1vw equals 1% of the viewport width. This means as the viewport width changes, the font size will change proportionally.
For example, setting the font size of h1 elements to 8% of the viewport width will result in a font size that's proportional to the viewport width. This means for viewports 500 pixels wide, the calculated font size would be 40px, which is within the 24px-48px min-max range specified.
You can also use the clamp function to set a minimum and maximum font size, so that the font size will never be too small or too large. This is especially useful for ensuring that your font sizes remain readable across different screen sizes.
The clamp function works by setting a minimum and maximum value for the font size, so that it will never exceed or fall below those values. For example, setting the font size of h1 elements to clamp(8vw, 24px, 48px) will ensure that the font size is between 24px and 48px, regardless of the viewport width.
Here are some common use cases for different CSS units:
- Use pixels when working with properties that aren’t really affected by responsiveness, like border-radius, box shadow, or border-width.
- Use rem when setting font sizes, especially for the root element, where the font size should be either 16px or 10px.
- Use em units when working with margins and paddings, as they relate to the parent element’s font size.
- Use percentages when working with widths and heights.
- Use vh and vw when working with elements that depend on the viewport of the website.
Viewport-Based Units
Viewport-Based Units are a powerful tool for creating responsive font sizes. They're relative to the size of the viewport, which is the visible part of a webpage.
The most common viewport-based units are vw and vh, which stand for viewport width and viewport height, respectively. One vw equals 1% of the width of the current viewport, while one vh equals 1% of the height of the viewport.
Using vw units for font size can lead to text that's ridiculously large or small on different devices, unless combined with other units. For example, setting font-size to 1.6vw can result in text that's 16 pixels large on a 1000-pixel wide browser, but only 5 pixels large on a 300-pixel mobile screen.
Viewport height is less frequently used than viewport width, but it's still a useful unit to know about. One vh equals 1% of the height of the viewport, making it a great choice for elements that need to be a specific percentage of the screen height.
To get a better sense of how viewport units work, consider this: 100vw is equivalent to 100% of the viewport width, and 50vh is equivalent to 50% of the viewport height. This makes it easy to calculate the size of elements based on the viewport size.
Design and Measurement Units
There are about 15 CSS units supported by modern browsers. CSS Units are classified into two groups: Absolute units and Relative units.
Absolute units, such as pixels (px) and points (pt), are fixed and don't change based on the user's device or settings. In contrast, Relative units, like ems and percentages, are relative to the parent element or the user's settings.
Understanding these units is crucial when working with responsive font sizes, as it allows you to create flexible and user-friendly designs.
Pixels (Px)
Pixels (Px) are fixed sizes, equal to one dot on the screen. This makes them a good choice for achieving a "pixel-perfect" rendition of web designs.
Pixels do not change size, which can be both good and bad. It's a bad thing because fonts will be rendered smaller on a higher resolution screen than on a lower resolution screen.
Pixels are often used in CSS font sizes because they allow for accurate rendering. This is particularly important for web developers who want to create a precise design.
A higher resolution screen will display pixels smaller than a lower resolution screen, which can affect font sizes. This is because pixels are fixed sizes and don't scale up or down.
Design Units
In design, it's essential to understand the different units used to measure and scale elements. There are about $15 CSS units/$ currently supported by modern browsers.
To make sense of these units, we need to classify them into two groups: Absolute units and Relative units. Absolute units are used to define specific values, such as pixels or points.
For example, pixels are a common Absolute unit used in web design. Points are also an Absolute unit, often used in print design.
Relative units, on the other hand, are used to define values relative to a parent element. Em and rem are two popular Relative units used in CSS.
In my experience, using Relative units can make it easier to scale designs across different devices and screen sizes.
Sources
- https://blog.hubspot.com/website/responsive-text
- https://pieces.app/blog/css-units-responsive-website-designs
- https://blog.dai.codes/responsive-css-without-media-queries/
- https://blueprintdigital.com/blog/font-sizes-in-responsive-design/
- https://stackoverflow.com/questions/15649244/responsive-font-size-in-css
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