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Added 29 Jul 2026
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input-underline
Underline Grow Input
Inputs & Hover

Underline Grow Input

Featured

Minimalist input whose bottom border grows in from the left on focus for an elegant material reveal.

Inputs & Hover
lines of CSS
28lines of CSS
dependencies
0dependencies
browser, for years
Everybrowser, for years
motion only on interaction
Hovermotion only on interaction
Backdrop
Open a live copy in

Vue, Svelte, styled-components and Tailwind exports are part of Pro. HTML, CSS and React are free forever.

input-underline.css
.fx-input-underline {
  position: relative;
  width: 100%;
  max-width: 260px;
}
.fx-input-underline input {
  width: 100%;
  padding: 0.6rem 0.25rem;
  border: none;
  border-bottom: 2px solid #cbd5e1;
  background: transparent;
  color: inherit;
  font-size: 1rem;
  outline: none;
}
.fx-input-underline::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 2px;
  background: #6366f1;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.35s ease;
}
.fx-input-underline:focus-within::after { transform: scaleX(1); }
input-underline.html
<div class="fx-input-underline">
  <input type="text" placeholder="Search…" />
</div>

What do I do with this?

  1. Put input-underline.css anywhere your page already loads CSS from — in Next.js that is app/globals.css, or any stylesheet with a <link> in your HTML.
  2. Then put the class on the element you want it on: <button class="fx-input-underline">. The CSS does nothing until a class name in it matches something on the page.
  • Link the stylesheet, then paste the markup wherever you need it.
npx hoverlab add input-underline

What's included

  • The markup and the stylesheet, in whichever framework you pick
  • No runtime dependencies

Works with

  • React
  • Vue
  • Svelte
  • Tailwind
  • styled-components
  • Plain CSS

npx hoverlab add input-underline

Or over MCP, from your editor's agent — no account needed.

License

Free to read, copy and install, for personal and non-commercial projects. Shipping it in client work or a paid product needs Pro ($79 once). The source lands in your repo and stops being ours — no attribution, nothing to upgrade.

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Motion safety

Static estimate, read from the CSS

Reduced motion
Brief motion, no guard

Animates briefly or on interaction. Only looping motion gets a guard in this catalog; copy the one from the Insights tab if this ships on a critical path.

What it animates
Compositor only

Only transform, opacity or filter: the GPU can run it without re-laying-out or repainting the page.

Flashing (WCAG 2.3.1)
No flashing found

No repeating change in opacity, colour or brightness large enough to count as a flash.

Layout shift (CLS)
No shift expected

Nothing it animates moves or resizes the box in flow. A category from the CSS, not a measurement for this effect.

Every row is read from the shipped CSS. Only a figure marked measured came from a browser. Customizing the speed changes the timing, so recheck a customized copy. How it is computed

38 more effects in Inputs & Hover

All of them free to read, copy and install — no account, no locked tiles, no watermarked preview. The whole catalog is open, and so are the API and the CLI.

Browse Inputs & Hover

Shipping one commercially

Copying the code is free. Putting it in client work or a paid product is what Pro is for — the licence, not the access.

  • A commercial licence for everything in the catalog
  • Unlimited bundle exports, in Vue, Svelte and Tailwind
  • One payment — no subscription, nothing to renew
Pro — $79 once

7 variations of Underline Grow Input

Finished looks, each one a position in the customizer above. Copy any of them, or open it and keep moving the sliders.