Modals and dialogs

Modals & Dialogs

Overview

Overlays interrupt — use them sparingly and correctly. shadcn/ui (on Radix) gives you four primitives with built-in focus trap, Esc to close, scroll lock, and aria-modal. Your job is choosing the right one and handling the edge cases: destructive confirms, forms with unsaved input, and not stacking overlays.

When to use

• A focused task or confirmation needs to block the page.
• Building a side panel for details/filters/quick-edit.
• A <div> overlay is being hand-rolled (you'll miss focus trap + keyboard).

Pick the right primitive

Use	Primitive	When
Centered modal	Dialog	Short forms, focused tasks
Side panel	Sheet	Details, filters, edit alongside context
Bottom drawer	Drawer (vaul)	Mobile-friendly, touch dismiss
Confirm/destruct	AlertDialog	Yes/no decisions; no dismiss-on-outside-click

Destructive confirmation

AlertDialog (not Dialog) for irreversible actions — it requires an explicit choice and won't close on outside click or Esc accidentally losing the decision:

<AlertDialog>
  <AlertDialogTrigger asChild>
    <Button variant="destructive">Delete project</Button>
  </AlertDialogTrigger>
  <AlertDialogContent>
    <AlertDialogHeader>
      <AlertDialogTitle>Delete this project?</AlertDialogTitle>
      <AlertDialogDescription>
        This permanently deletes the project and all its data. This can’t be undone.
      </AlertDialogDescription>
    </AlertDialogHeader>
    <AlertDialogFooter>
      <AlertDialogCancel>Cancel</AlertDialogCancel>
      <AlertDialogAction
        className="bg-destructive text-destructive-foreground hover:bg-destructive/90"
        onClick={deleteProject}
      >
        Delete
      </AlertDialogAction>
    </AlertDialogFooter>
  </AlertDialogContent>
</AlertDialog>

For high-risk deletes, require typing the resource name to enable the button.

Forms inside dialogs

Control open so you can keep the dialog open on validation error and close only on success:

const [open, setOpen] = React.useState(false);
async function onSubmit(values) {
  await save(values);     // throws → dialog stays open, error shows
  setOpen(false);         // success → close
  toast.success("Saved");
}
<Dialog open={open} onOpenChange={setOpen}>…</Dialog>

Warn before discarding unsaved changes: intercept onOpenChange and confirm if the form isDirty.

Accessibility (mostly handled, don't break it)

• Always include DialogTitle (+ DialogDescription) — they back aria-labelledby/describedby. Visually hide the title with sr-only if needed, but keep it.
• Focus moves into the dialog on open and returns to the trigger on close — don't disable this.
• Don't stack modals. Replace content or use a multi-step flow instead.

Pitfalls

• Dialog for destructive actions — outside-click dismiss can skip the decision; use AlertDialog.
• Closing on submit before the request resolves — close on success only.
• No unsaved-changes guard — users lose form input on accidental dismiss.
• Missing DialogTitle — breaks the accessible name; Radix will warn.
• Modal-on-modal stacking — confusing focus; redesign the flow.
• Putting huge content in a modal — use a Sheet or a full page instead.

Hand-off

Overlays that host forms-and-validation, confirm data-tables row actions, and pair with notifications-and-toasts for post-action feedback.