Form

Put server-side errors back onto the fields they came from. Custom element

Choosing between components

Reach for Form only when errors arrive from somewhere the browser cannot see — a server response, an async uniqueness check. Everything a required, a type="email", or a pattern can decide is already decided by native constraint validation, and adding Form does not change it.

Markup you author

Author an empty error part inside each field wrapper. Form resolves it as the single error part in the nearest wrapper holding no other named control, which is the shape .ui-field, .ui-choice-group, and .ui-fieldset already produce, then writes the message and points the field’s aria-describedby at it. A field with no wrapper gets no error element rather than someone else’s.

Form

Copy this markup

<ui-form>
  <form class="ui-form-demo-stack" id="workspace-form" action="#workspace" method="post" data-ui-part="form">
    <div class="ui-field">
      <label class="ui-label" for="workspace-slug">Workspace address</label>
      <div data-ui-part="control">
        <input class="ui-input" id="workspace-slug" name="slug" type="text" value="acme" aria-describedby="workspace-slug-description">
        <p class="ui-description" id="workspace-slug-description">Lowercase letters, numbers, and hyphens.</p>
        <p class="ui-error" data-ui-part="error"></p>
      </div>
    </div>
    <div class="ui-field">
      <label class="ui-label" for="workspace-owner">Owner email</label>
      <div data-ui-part="control">
        <input class="ui-input" id="workspace-owner" name="owner" type="email" value="ops@acme.test">

        <p class="ui-error" data-ui-part="error"></p>
      </div>
    </div>
    <div class="ui-form-demo-actions">
      <button class="ui-button" data-ui-variant="primary" id="workspace-save" type="button">Save</button>
      <button class="ui-button" data-ui-variant="secondary" id="workspace-clear" type="button">Clear errors</button>
    </div>
  </form>
</ui-form>

Install

Styles and registration

import '@timelessui/components/css/tokens.css'
import '@timelessui/components/css/core/form.css'
import '@timelessui/components/css/core/forms.css'
import '@timelessui/components/css/core/button.css'
import '@timelessui/components/css/themes/atmosphere/tokens.css'
import '@timelessui/components/css/themes/atmosphere/forms.css'
import '@timelessui/components/css/themes/atmosphere/button.css'
import '@timelessui/components/register/ui-form'

A register/ import is a side effect: it defines the element as the module evaluates, so it has to run in code the browser loads. To register explicitly instead — to control the timing, or to define into another window — call the function from the matching define/ entry point, which registers nothing on its own:

Explicit registration

import { defineFormElement } from '@timelessui/components/define/ui-form'
defineFormElement()

Consumer wiring

This example needs the following plain JavaScript beyond custom-element registration.

const form = document.querySelector('ui-form')
if (form) {
  document.getElementById('workspace-save')?.addEventListener('click', () => {
    form.setErrors({
      slug: 'That workspace address is already taken.',
      owner: 'No account exists for this address.',
    })
  })
  document.getElementById('workspace-clear')?.addEventListener('click', () => form.clearErrors())
}

Anatomy

Parts are authored in your own markup and identified by the selector below, so your CSS can target the same anatomy without loading Timeless styles. Required parts must be present for the component to work. Private data-ui-internal-* hooks are written by the runtime and must never be authored.

<ui-form>

Part	Required	Selector	Purpose
form	Yes	form	The native <form>. Submission, method, action, reset, and constraint validation are all still its job; ui-form only writes messages onto the fields inside it.
error	No	[data-ui-part~='error']	The message element for one field, resolved as the single error part inside the nearest wrapper that holds no other named control. .ui-field, .ui-choice-group, and .ui-fieldset all produce that shape, so no pairing attribute is needed. ui-form writes its text and points the field’s aria-describedby at it.

ui-field

Part	Required	Selector	Purpose
control	No	[data-ui-part~='control']	Wrapper around the native control when one is needed.

Attributes

Every value below is implemented by the stylesheets this component ships. Boolean attributes are presence-based: author the attribute with no value, or omit it.

ui-field

Attribute	Values	Default	Description
data-ui-layout	stacked · inline	stacked	Whether the label sits above the control or beside it.
data-ui-density	compact · normal · spacious	normal	Gap between label, control, description, and error.

ui-input

Attribute	Values	Default	Description
data-ui-size	sm · md · lg	md	Control height, padding, and font size.

Element API

Attributes above are the authoring surface. These are the DOM properties and events the registered element adds once it upgrades.

<ui-form>

This element adds no public properties. Configure it with its attributes.

Event	Detail	Description
ui-invalid	CustomEvent<FormInvalidDetail>	Dispatched after setErrors has put at least one message on a control, naming the fields that matched. Clearing errors dispatches nothing.

State

Native attributes, ARIA, and platform pseudo-classes are authoritative. Style state through the selectors below rather than adding your own state classes.

State	Source	How to express it
invalid	aria	Set aria-invalid="true" on the control and point aria-describedby at the error part.
invalid	native	Native :invalid, or aria-invalid="true".
disabled	native	Native disabled.

Styling

Root identity: ui-form, ui-field, ui-label, ui-input, ui-description, ui-error. Required stylesheets: tokens.css, core/form.css, core/forms.css, core/button.css, themes/atmosphere/tokens.css, themes/atmosphere/forms.css, themes/atmosphere/button.css.

This component adds no custom properties of its own. Restyle it through the design tokens or your own CSS.

Design tokens this component reads (39)

These are global Atmosphere tokens. Change them once at the theme level rather than per component.

--ui-accent · --ui-bg-accent · --ui-bg-accent-active · --ui-bg-accent-hover · --ui-bg-control · --ui-bg-control-active · --ui-bg-control-hover · --ui-bg-control-muted · --ui-bg-danger · --ui-bg-danger-active · --ui-bg-danger-hover · --ui-bg-surface · --ui-bg-surface-subtle · --ui-danger · --ui-danger-soft · --ui-disabled-opacity · --ui-duration-fast · --ui-ease-standard · --ui-fg · --ui-fg-muted · --ui-fg-subtle · --ui-focus · --ui-line · --ui-line-strong · --ui-radius-control · --ui-radius-md · --ui-radius-pill · --ui-radius-sm · --ui-shadow-control · --ui-shadow-control-accent · --ui-shadow-control-active · --ui-shadow-control-danger · --ui-shadow-inset · --ui-shadow-outline-control · --ui-space-1 · --ui-space-2 · --ui-space-3 · --ui-space-4 · --ui-space-5

Accessibility

Keep the native elements, roles, and relationships shown in the example. Timeless adds only the state and keyboard coordination the platform does not already provide, and it never supplies your accessible names — those depend on your content.

The ARIA Authoring Practices Guide has no pattern for Form errors. The contract below is a composition of behavior the platform already defines, not ARIA invented to fill the gap.

There is no APG pattern for server-side error mapping. ui-form sets aria-invalid on each field it marks and points aria-describedby at the authored error text, then moves focus to the first field that took a message — which is what makes the error reachable rather than merely visible. Everything else, including the native validation bubble, stays with the platform.

Verify in context

Automated checks cover axe WCAG 2.2 A and AA rules on every documented route. Keyboard, zoom, forced-colors, and screen-reader review still belong to your application.

Before JavaScript runs

The markup above is complete and usable on its own: native controls submit, labels associate, and authored ARIA is already correct. Registration adds state synchronisation, focus management, and keyboard coordination on top of it.

More examples

Open Form in StoryLite for variants, controls, and manual testing.