# Auto-growing text area

> Starts as a single line, grows with every new line you write and its focus ring gently breathes.

- Category: [Inputs](https://library.aimran.es/components/inputs)
- Built with: HTML + CSS
- Live editor: https://library.aimran.es/blocks/uv-in2-grow
- Library: AIMRAN Library (https://library.aimran.es), free, no sign-up, by Aimran Oukham

## Where to use it

A text box that grows as you write feels lighter than a big empty rectangle, which makes people more willing to start. Good spots for it: the comment box under a blog post, the message field of a support chat or the notes of a booking form. An auto-resize textarea in HTML and CSS, with a few lines of JavaScript.

It works best for short to medium messages. For long texts such as a cover letter or a detailed complaint, start with a taller box so the page does not keep jumping while people type.

## Code

### HTML

```html
<label class="uv-in2gr"><textarea rows="1" placeholder="Tell me something…"></textarea></label>
```

### CSS

```css
.uv-in2gr {
  --c1: #0071e3;
  --c2: #8ec5ff;
  --s: 16px;
  /* tamaño */
  --k: 1;
  /* velocidad */
  --fg: #1d1d1f;
  /* texto */
  --bg: #f5f5f7;
  /* fondo */
}

.uv-in2gr {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  font-size: var(--s);
  color: var(--fg);
  -webkit-tap-highlight-color: transparent;
  display: block;
  width: 17em;
}

.uv-in2gr textarea {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  width: 100%;
  box-sizing: border-box;
  min-height: 3em;
  padding: .9em 1em;
  font-size: var(--s);
  line-height: 1.45;
  color: var(--fg);
  background: color-mix(in srgb,var(--fg) 5%,transparent);
  border: 0;
  outline: 0;
  border-radius: .95em;
  resize: none;
  overflow: hidden;
  box-shadow: inset 0 0 0 1.6px color-mix(in srgb,var(--fg) 10%,transparent);
  transition: box-shadow calc(0.3s / var(--k)) cubic-bezier(.25,.1,.25,1),height calc(0.2s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-in2gr textarea:focus {
  animation: uv-in2gr calc(2.4s / var(--k)) cubic-bezier(.25,.1,.25,1) infinite;
}

@keyframes uv-in2gr {
  0%,100% {
    box-shadow: inset 0 0 0 1.8px var(--c1),0 0 0 3px color-mix(in srgb,var(--c1) 16%,transparent);
  }
  50% {
    box-shadow: inset 0 0 0 1.8px var(--c1),0 0 0 8px color-mix(in srgb,var(--c1) 5%,transparent);
  }
}
```

### JavaScript

```js
document.querySelectorAll(".uv-in2gr").forEach(el => {
  const t=el.querySelector("textarea");const fit=()=>{t.style.height="auto";t.style.height=t.scrollHeight+"px"};t.addEventListener("input",fit);fit()
});
```

### React

```tsx
// @ts-nocheck: setup() es JavaScript del DOM sin tipos, el mismo de la pestaña JS.
import { useEffect, useRef, type CSSProperties } from "react";

const css = `
.uv-in2gr {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  font-size: var(--s);
  color: var(--fg);
  -webkit-tap-highlight-color: transparent;
  display: block;
  width: 17em;
}

.uv-in2gr textarea {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  width: 100%;
  box-sizing: border-box;
  min-height: 3em;
  padding: .9em 1em;
  font-size: var(--s);
  line-height: 1.45;
  color: var(--fg);
  background: color-mix(in srgb,var(--fg) 5%,transparent);
  border: 0;
  outline: 0;
  border-radius: .95em;
  resize: none;
  overflow: hidden;
  box-shadow: inset 0 0 0 1.6px color-mix(in srgb,var(--fg) 10%,transparent);
  transition: box-shadow calc(0.3s / var(--k)) cubic-bezier(.25,.1,.25,1),height calc(0.2s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-in2gr textarea:focus {
  animation: uv-in2gr calc(2.4s / var(--k)) cubic-bezier(.25,.1,.25,1) infinite;
}

@keyframes uv-in2gr {
  0%,100% {
    box-shadow: inset 0 0 0 1.8px var(--c1),0 0 0 3px color-mix(in srgb,var(--c1) 16%,transparent);
  }
  50% {
    box-shadow: inset 0 0 0 1.8px var(--c1),0 0 0 8px color-mix(in srgb,var(--c1) 5%,transparent);
  }
}
`;

// Interacción en JavaScript del DOM: la misma que en la pestaña JS.
// eslint-disable-next-line @typescript-eslint/no-explicit-any
function setup(el: any) {
  const t=el.querySelector("textarea");const fit=()=>{t.style.height="auto";t.style.height=t.scrollHeight+"px"};t.addEventListener("input",fit);fit()
}

export default function In2Grow() {
  const ref = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const el = ref.current?.firstElementChild;
    return el ? setup(el) : undefined;
  }, []);

  return (
    <>
      <style>{css}</style>
      <div
        ref={ref} style={{
          "--c1": "#0071e3",
          "--c2": "#8ec5ff",
          "--s": "16px",
          "--k": "1",
          "--fg": "#1d1d1f",
          "--bg": "#f5f5f7",
        } as CSSProperties}
      >
        <label className="uv-in2gr"><textarea rows={1} placeholder="Tell me something…"></textarea></label>
      </div>
    </>
  );
}
```

## Prompt for AI assistants

Paste this into ChatGPT, Claude, Cursor, v0 or Lovable to adapt the block to your stack (Tailwind, Vue, Svelte…):

````text
I want to add the “Auto-growing text area” block (Inputs) from AIMRAN Library to my project.

## What it is
Starts as a single line, grows with every new line you write and its focus ring gently breathes.

## Chosen settings
- Main color: #0071e3
- Secondary color: #8ec5ff
- Size: 16px (from 12 to 24px)
- Speed: 1x (from 0.5 to 2x)
- Text: "Tell me something…"

## What I need
1. Add it to my project with the same look and animation as the reference code: same sizes, colours, radii, shadows, timings and easing.
2. It is built with plain HTML and CSS (the reference wraps it in a React component with its CSS). If my project uses something else (Vue, Svelte, Astro, plain HTML…), translate it without losing any behaviour. If I use Tailwind, turn the styles into classes; if not, keep the CSS in its own file.
3. Expose the settings above as props (or CSS variables) with those values as defaults.
4. Make it work well on phones: nothing that depends only on hover, touch targets of at least 44 px and no overflow on 320 px screens.
5. Make it look right in light and dark mode.
6. Keep it accessible: semantic HTML, roles and aria-* where needed, visible focus and keyboard support.
7. Respect prefers-reduced-motion: with reduced motion, no big animations but the same end result.

## Reference code
```tsx
// @ts-nocheck: setup() es JavaScript del DOM sin tipos, el mismo de la pestaña JS.
import { useEffect, useRef, type CSSProperties } from "react";

const css = `
.uv-in2gr {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  font-size: var(--s);
  color: var(--fg);
  -webkit-tap-highlight-color: transparent;
  display: block;
  width: 17em;
}

.uv-in2gr textarea {
  font-family: -apple-system,BlinkMacSystemFont,"SF Pro Text","Inter",system-ui,sans-serif;
  width: 100%;
  box-sizing: border-box;
  min-height: 3em;
  padding: .9em 1em;
  font-size: var(--s);
  line-height: 1.45;
  color: var(--fg);
  background: color-mix(in srgb,var(--fg) 5%,transparent);
  border: 0;
  outline: 0;
  border-radius: .95em;
  resize: none;
  overflow: hidden;
  box-shadow: inset 0 0 0 1.6px color-mix(in srgb,var(--fg) 10%,transparent);
  transition: box-shadow calc(0.3s / var(--k)) cubic-bezier(.25,.1,.25,1),height calc(0.2s / var(--k)) cubic-bezier(.25,.1,.25,1);
}

.uv-in2gr textarea:focus {
  animation: uv-in2gr calc(2.4s / var(--k)) cubic-bezier(.25,.1,.25,1) infinite;
}

@keyframes uv-in2gr {
  0%,100% {
    box-shadow: inset 0 0 0 1.8px var(--c1),0 0 0 3px color-mix(in srgb,var(--c1) 16%,transparent);
  }
  50% {
    box-shadow: inset 0 0 0 1.8px var(--c1),0 0 0 8px color-mix(in srgb,var(--c1) 5%,transparent);
  }
}
`;

// Interacción en JavaScript del DOM: la misma que en la pestaña JS.
// eslint-disable-next-line @typescript-eslint/no-explicit-any
function setup(el: any) {
  const t=el.querySelector("textarea");const fit=()=>{t.style.height="auto";t.style.height=t.scrollHeight+"px"};t.addEventListener("input",fit);fit()
}

export default function In2Grow() {
  const ref = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const el = ref.current?.firstElementChild;
    return el ? setup(el) : undefined;
  }, []);

  return (
    <>
      <style>{css}</style>
      <div
        ref={ref} style={{
          "--c1": "#0071e3",
          "--c2": "#8ec5ff",
          "--s": "16px",
          "--k": "1",
          "--fg": "#1d1d1f",
          "--bg": "#f5f5f7",
        } as CSSProperties}
      >
        <label className="uv-in2gr"><textarea rows={1} placeholder="Tell me something…"></textarea></label>
      </div>
    </>
  );
}
```

Give me the complete final code, ready to paste, and tell me in one line where to put it in my project.
````