modern-css.com valid

modern-css.com

Every old CSS hack next to its clean, modern replacement. The old way and the modern way, side by side.

For agents: Reference site pairing old CSS hacks with their modern replacements, showing the outdated way and the current way side by side.

csscss hacksmodern cssweb developmentcss reference

Their llms.txt

The beginning of the file, from our validated copy saved 2026-10-21T14:46:29.528Z. Cached copy · Source on modern-css.com

# modern-css.com

> Every old CSS hack next to its clean, modern replacement. The old way and the modern way, side by side.

modern-css.com is a reference site for web developers. It shows side-by-side comparisons of outdated CSS patterns and their modern native replacements, plus in-depth tutorials and a curated resource directory.

Full content (all 117 snippets with explanations and code): https://modern-css.com/llms-full.txt

## Content

Each comparison includes:
- The old approach (what developers used before)
- The modern approach (what native CSS supports now)
- A live interactive demo
- Browser support data with Baseline status (widely/newly/limited availability)
- MDN documentation links and caniuse.com links
- Polyfill links where available
- A plain-language explanation of how the modern approach works

Snippets can be filtered by Baseline availability status on the home and category pages.

## Topics covered

- Centering elements: absolute + transform vs grid place-items
- Overflow-safe centering: media query flex-start vs justify-content: safe center
- Parent selection: JavaScript closest() vs CSS :has()
- Color mixing: Sass mix() vs native color-mix()
- Responsive components: @media vs @container queries
- Selector nesting: Sass/Less vs native CSS nesting
- Scroll animations: IntersectionObserver vs animation-timeline
- Sticky headers: JavaScript scroll listeners vs position: sticky
- Aspect ratios: padding-top hack vs aspect-ratio property
- Spacing elements: margin hacks vs gap property
- Fluid typography: media query breakpoints vs clamp()
- Theme variables: Sass variables vs CSS custom properties
- Specificity control: !important vs @layer cascade layers
- Focus styles: :focus vs :focus-visible
- Selector grouping: repetition vs :is()
- Form controls: appearance: none rebuild vs accent-color
- Nested grids: duplicate tracks vs subgrid
- Masonry layouts: Masonry.js / column-count vs display: grid-lanes
- Grid areas: line numbers vs grid-template-areas
- Direction-aware layouts: left/right vs logical properties
- Low-specificity resets: tricks vs :where()
- Dark mode colors: duplicate values vs light-dark()
- Dark mode defaults: manual styles vs color-scheme
- Variable fonts: multiple files vs one variable font
- Font loading: FOIT vs font-display: swap
- Balanced headlines: manual breaks vs text-wrap: balance
- Scroll snapping: JS carousel vs scroll-snap
- Page transitions: JS framework vs View Transitions API
- Entry animations: JS timing vs @starting-style
- Display none animation: JS workarounds vs transition-behavior: allow-discrete
- Independent transforms: shorthand vs separate properties
- Typed custom properties: untyped vs @property
- Scoped styles: BEM naming vs @scope
- Tooltip positioning: Popper.js vs CSS anchor positioning
- Dropdown menus: JS toggles vs popover API
- Flipping tooltips: JS overflow checks and flip logic vs position-try-fallbacks
- Dropdown width: measuring the button in JS vs anchor-size()
…

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