UI language

The <Designer> speaks English by default. Pass locale="pt-BR" to switch its own UI (buttons, tabs, warnings, placeholders) to Portuguese:

<Designer
  locale="pt-BR"
  template={template}
  onChangeTemplate={setTemplate}
  bindings={bindings}
  onChangeBindings={setBindings}
/>

This is purely a UI-chrome setting — it never changes how the generated PDF formats dates or currency (that's {DATE(...)}/ {CURRENCY(...)} written into the template's own content by whoever designs it, see Data binding), and it never changes the internal name your templates already use for existing fields.

Standalone components

If you use any of the package's components standalone (PdfPreview, FieldList, etc.) without wrapping them in <Designer>, they render in English by default too — wrap them in <I18nProvider locale="pt-BR"> yourself if you need them in Portuguese:

import { I18nProvider } from "json-pdf-designer";
import { PdfPreview } from "json-pdf-designer/preview";

<I18nProvider locale="pt-BR">
  <PdfPreview bytes={pdfBytes} />
</I18nProvider>

useT()/useLocale() (exported) give you the active dictionary/locale code inside your own components — the same context <Designer> uses internally.