Modern CSS in 2025: 6 Snippets You Should Know

6 CSS Snippets Every Front-End Developer Should Know In 2025

TLDR: This article presents six powerful CSS snippets that every front-end developer should know in 2025. These snippets cover new features like view transitions, linear() easing, typed custom properties, and animations for <dialog>, [popover], and <details>.

Summary: As CSS continues to evolve, it's important for front-end developers to stay up-to-date with the latest features and techniques. This article provides a practical guide to six modern CSS snippets that can help you create more engaging and interactive user experiences.

The first snippet covers linear() easing, a new way to create springy and bouncy animations that feel more natural than traditional easing functions. The article also introduces typed custom properties using @property, which allow you to create more robust and animatable CSS systems.

The third snippet is a simple one-liner for enabling cross-fade page transitions with the View Transitions API. This is a powerful feature that can add a touch of polish to your multi-page applications.

The article then dives into how to create transition animations for the <dialog> and [popover] elements, which are now first-class citizens in the browser's top layer. It also covers how to animate the <details> element, a long-awaited feature that is now possible with interpolate-size.

Finally, the article shows how to create animated, adaptive gradient text that responds to light and dark themes. This is a great way to add a bit of flair to your headlines and other text elements.

For front-end developers, this article is a treasure trove of modern CSS techniques that you can start using today. The snippets are well-explained and come with links to additional resources and demos.

Key takeaways:

• linear() easing allows for more natural and springy animations.
• Typed custom properties with @property make CSS systems more robust and animatable.
• View Transitions can be enabled with a single line of CSS.
• You can now create transition animations for <dialog>, [popover], and <details>.
• Animated, adaptive gradient text is a great way to add visual interest to your text.

Link: 6 CSS Snippets Every Front-End Developer Should Know In 2025

What You Need to Know about Modern CSS (2025 Edition)

TLDR: This article provides a comprehensive overview of the most important new features in CSS for 2025. It covers everything from animating to auto, popovers and invokers, custom functions with @function, and the new if() function.

Summary: CSS is evolving at a rapid pace, and it can be hard to keep up with all the new features. This article provides a curated list of the most important things you need to know about modern CSS in 2025.

The article starts with a look at how to animate to auto height, a long-standing problem in CSS that can now be solved with the interpolate-size property. It then moves on to popovers and invokers, new HTML attributes that provide a declarative way to create and control popover elements.

The article also introduces two powerful new features for CSS functions: @function and if(). @function allows you to create your own custom CSS functions, while if() provides a way to add conditional logic to your styles.

Other new features covered in the article include field-sizing for creating auto-growing form fields, custom selects for styling the <select> element, text-wrap for better typography, linear() easing for more natural animations, and the new shape() function for creating complex shapes.

For front-end developers, this article is an essential guide to the latest and greatest in CSS. It provides a clear and concise overview of the most important new features, with links to additional resources and demos.

Key takeaways:

• You can now animate to auto height in CSS.
• Popovers and invokers provide a declarative way to create and control popovers.
• You can create your own custom CSS functions with @function.
• The if() function allows you to add conditional logic to your styles.
• Other new features include field-sizing, custom selects, text-wrap, linear() easing, and shape().

Link: What You Need to Know about Modern CSS (2025 Edition)

Default styles for h1 elements are changing

TLDR: Browsers are starting to remove the default UA styles that change the font size of <h1> elements based on how deeply they are nested within sectioning elements. Developers should check their sites to make sure they are not relying on these default styles.

Summary: For a long time, the HTML spec defined an "outline algorithm" that would give <h1> elements a different heading level (and therefore a different font size) depending on how many <section>, <aside>, <nav>, or <article> elements they were nested inside. This feature was often a source of confusion for developers, and it has now been removed from the HTML spec.

As a result, browsers are starting to remove the corresponding UA stylesheet rules that implemented this behavior. This means that <h1> elements will no longer automatically change their font size based on their nesting level.

This article explains what is changing, when to expect the changes in different browsers, and what to do if your site is affected. It also provides some tips for creating more robust and conformant heading structures.

The main takeaway for developers is that you should not rely on default browser styles to convey heading hierarchy. You should always explicitly define your heading levels using <h2>, <h3>, etc., and you should always define your own font-size and margin for <h1> elements.

Key takeaways:

• Browsers are removing the default styles that change the font size of nested <h1> elements.
• You should not rely on default browser styles for heading hierarchy.
• Always define your own font-size and margin for <h1> elements.
• Audit your site using Lighthouse to check for deprecated usage.

Link: Default styles for h1 elements are changing | MDN Blog