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Added 17 Aug 2026
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underline-grow-field-15291
Underline Grow Field
Forms & Validation

Underline Grow Field

Borderless field with a thin bottom rule where an accent underline grows outward from the centre on focus.

Forms & Validationinputunderlinefocusminimal
lines of CSS
29lines 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.

underline-grow-field-15291.css
.fx-v12-fm-underline-15290 {
  position: relative;
  display: block;
  width: 220px;
  font-family: system-ui, sans-serif;
}
.fx-v12-fm-underline-15290 span { display: block; font-size: 0.68rem; letter-spacing: 0.06em; text-transform: uppercase; color: #64748b; margin-bottom: 2px; transition: color 0.25s ease; }
.fx-v12-fm-underline-15290 input {
  width: 100%;
  box-sizing: border-box;
  padding: 0.4rem 0;
  font-size: 0.95rem;
  color: #e2e8f0;
  background: transparent;
  border: none;
  border-bottom: 1.5px solid #334155;
  outline: none;
}
.fx-v12-fm-underline-15290 i {
  position: absolute;
  left: 50%; right: 50%;
  bottom: 0;
  height: 2px;
  background: #10b981;
  transition: left 0.3s ease, right 0.3s ease;
}
.fx-v12-fm-underline-15290:hover i { left: 40%; right: 40%; }
.fx-v12-fm-underline-15290:focus-within i { left: 0; right: 0; }
.fx-v12-fm-underline-15290:focus-within span { color: #34d399; }
underline-grow-field-15291.html
<label class="fx-v12-fm-underline-15290">
  <span>Full name</span>
  <input type="text" value="Ada Lovelace" />
  <i></i>
</label>

What do I do with this?

  1. Put underline-grow-field-15291.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-v12-fm-underline-15290">. 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 underline-grow-field-15291

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 underline-grow-field-15291

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
Reflows

Animates left, right (and color). The browser re-lays-out the page on every frame; prefer transform if you can.

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)
May shift layout

Animates left, right on a box in flow, so content beside or after it can move. 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

33 more effects in Forms & Validation

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 Forms & Validation

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 Field

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