> ## Documentation Index
> Fetch the complete documentation index at: https://prefab.prefect.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Label
> Labels identify form inputs and controls.
export const ComponentPreview = ({json, height, resizable, bare, hideJson, playground, children}) => {
const hostRef = React.useRef(null);
const handleRef = React.useRef(null);
const cardRef = React.useRef(null);
const containerRef = React.useRef(null);
const [previewWidth, setPreviewWidth] = React.useState(null);
const [isDragging, setIsDragging] = React.useState(false);
const [playgroundHref, setPlaygroundHref] = React.useState(null);
React.useEffect(function () {
if (!playground) return;
var isLocal = location.hostname === "localhost" || location.hostname === "127.0.0.1";
var path = isLocal ? "/playground" : "/docs/playground";
var url = new URL(path, window.location.href);
url.hash = "code=" + playground;
setPlaygroundHref(url.href);
}, [playground]);
var jsonStr = typeof json === "string" ? json : JSON.stringify(json, null, 2);
React.useEffect(function () {
if (cardRef.current) {
var card = cardRef.current.closest(".group");
if (card) card.classList.remove("group");
}
var host = hostRef.current;
if (!host || !json) return;
function mount() {
if (!window.__prefab || !host) return;
var dark = document.documentElement.classList.contains("dark");
handleRef.current = window.__prefab.mountPreview(host, jsonStr, {
dark: dark
});
if (bare && host.shadowRoot) {
var m = host.shadowRoot.querySelector("[data-prefab-mount]");
if (m) m.style.background = "transparent";
}
}
if (window.__prefab) {
mount();
} else {
if (!window.__prefabLoading) {
if (!window.__prefabReady) {
var s = document.createElement("script");
s.src = "/renderer.js";
document.head.appendChild(s);
}
window.__prefabLoading = new Promise(function (resolve) {
function check() {
if (window.__prefabReady) {
window.__prefabReady.then(resolve);
} else {
setTimeout(check, 10);
}
}
check();
});
}
window.__prefabLoading.then(mount);
}
var observer = new MutationObserver(function () {
var dark = document.documentElement.classList.contains("dark");
if (handleRef.current) handleRef.current.setDark(dark);
});
observer.observe(document.documentElement, {
attributes: true,
attributeFilter: ["class"]
});
return function () {
observer.disconnect();
if (handleRef.current) {
handleRef.current.unmount();
handleRef.current = null;
}
};
}, [json]);
function startResize(e) {
e.preventDefault();
var startX = e.clientX;
var startW = hostRef.current ? hostRef.current.offsetWidth : 0;
var maxW = containerRef.current ? containerRef.current.offsetWidth - 10 : startW;
setIsDragging(true);
function onMove(ev) {
var w = Math.max(260, Math.min(startW + (ev.clientX - startX), maxW));
setPreviewWidth(w);
}
function onUp() {
document.removeEventListener("mousemove", onMove);
document.removeEventListener("mouseup", onUp);
setIsDragging(false);
}
document.addEventListener("mousemove", onMove);
document.addEventListener("mouseup", onUp);
}
if (bare) {
return ;
}
if (resizable) {
return
{previewWidth &&
{previewWidth}px
}
{playgroundHref && }
{children}
;
}
return
{playgroundHref && }
{children}
;
};
Labels provide accessible text descriptions for form fields.
## Basic Usage
Labels can contain text directly or wrap other components.
```python Python icon="python" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
from prefab_ui.components import Label
Label("Email address")
```
```json Protocol icon="brackets-curly" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
{"view": {"type": "Label", "text": "Email address", "optional": false}}
```
## With Form Fields
Labels are typically paired with inputs and other form controls:
```python Python icon="python" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
from prefab_ui.components import (
Column,
Input,
Label,
)
with Column(gap=2):
Label("Username", for_id="username")
Input(placeholder="Enter username", name="username")
```
```json Protocol icon="brackets-curly" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
{
"view": {
"cssClass": "gap-2",
"type": "Column",
"children": [
{"type": "Label", "text": "Username", "forId": "username", "optional": false},
{
"name": "username",
"type": "Input",
"inputType": "text",
"placeholder": "Enter username",
"disabled": false,
"readOnly": false,
"required": false
}
]
}
}
```
## Optional Indicator
Set `optional=True` to show a muted "optional" hint after the label text. `Form.from_model()` sets this automatically for non-required fields; for manually built forms, set it yourself on any label.
```python Python icon="python" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
from prefab_ui.components import Column, Input, Label
with Column(gap=2):
Label("Phone", optional=True)
Input(input_type="tel", name="phone", placeholder="+1 (555) 000-0000")
```
```json Protocol icon="brackets-curly" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
{
"view": {
"cssClass": "gap-2",
"type": "Column",
"children": [
{"type": "Label", "text": "Phone", "optional": true},
{
"name": "phone",
"type": "Input",
"inputType": "tel",
"placeholder": "+1 (555) 000-0000",
"disabled": false,
"readOnly": false,
"required": false
}
]
}
}
```
## API Reference
Label text content. Can be passed as a positional argument.
ID of the associated form field element.
When `True`, displays a muted "optional" indicator after the label text.
Additional Tailwind CSS classes appended to the component's built-in styles.
## Protocol Reference
```json Label theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
{
"type": "Label",
"id?": "string",
"onMount?": "any",
"children?": "[Component]",
"let?": "object",
"text?": "string",
"forId?": "string",
"optional?": false,
"cssClass?": "string"
}
```
For the complete protocol schema, see [Label](/protocol/label).