# Classic Checkbox

> The everyday checkbox, finished properly: a hairline box that firms up on hover, a primary fill with a tick that draws itself in, a dash for the mixed state, a press that gives, and invalid and disabled styles. Three sizes, an optional label and description, built on Base UI so it submits with forms.

- Slug: `classic-checkbox`
- Category: [Checkboxes](https://www.assembli.design/category/checkboxes.md)
- Type: component
- Tags: checkbox, form, indeterminate, select-all, shadcn, base-ui
- npm dependencies: @base-ui/react
- shadcn/ui dependencies: none
- Added: 2026-10-22
- Live preview: https://www.assembli.design/preview/classic-checkbox
- Page: https://www.assembli.design/components/classic-checkbox

## 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/classic-checkbox/classic-checkbox.tsx` and installs dependencies):

```bash
npx shadcn@latest add @assembli/classic-checkbox
```

Registry item JSON: https://www.assembli.design/r/classic-checkbox.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.