# Autosize Textarea

> A textarea that grows with what you write, from a minimum to a maximum number of rows, then scrolls. Its footer holds your tools, a ring that fills toward a soft character limit (the count appears near the end and goes negative past it), and an optional send button that also answers ⌘/Ctrl+Enter and shows a spinner while an async submit runs.

- Slug: `autosize-textarea`
- Category: [Inputs](https://www.assembli.design/category/inputs.md)
- Type: component
- Tags: textarea, autosize, auto-grow, composer, character-limit, comment
- npm dependencies: lucide-react
- shadcn/ui dependencies: none
- Added: 2026-10-23
- Live preview: https://www.assembli.design/preview/autosize-textarea
- Page: https://www.assembli.design/components/autosize-textarea

## Install

One-time setup (needs a subscription):

1. Add the registry to the project's `components.json`: `{"@assembli":{"url":"https://www.assembli.design/r/{name}.json","headers":{"Authorization":"Bearer ${ASSEMBLI_API_KEY}"}}}` (merge into `"registries"`).
2. Put an API key from https://www.assembli.design/account in `.env.local` as `ASSEMBLI_API_KEY=asm_…`.

Then install with the shadcn CLI (writes `components/autosize-textarea/autosize-textarea.tsx` and installs dependencies):

```bash
npx shadcn@latest add @assembli/autosize-textarea
```

Registry item JSON: https://www.assembli.design/r/autosize-textarea.json (send `Authorization: Bearer <api key>`)

## Code

> Component source needs an Assembli subscription ($12/month) and an API key sent as `Authorization: Bearer <key>`. To get one without copying anything, POST https://www.assembli.design/api/agent/login (or call the MCP tool connect_account), show the user the link it returns, and poll https://www.assembli.design/api/agent/token for the key. Or subscribe at https://www.assembli.design/pricing and create a key at https://www.assembli.design/account.