Start with the packages in Getting Started. Install @tiptap/extension-text-style at the same version as your other Tiptap packages. This complete example registers the feature and renders its UI. In an existing editor, merge the imports and extension entries into your setup, and place the controls inside your existing RichTextProvider.

tsx

'use client';

import { EditorContent, useEditor } from '@tiptap/react';
import { Document } from '@tiptap/extension-document';
import { Paragraph } from '@tiptap/extension-paragraph';
import { Text } from '@tiptap/extension-text';
import { RichTextProvider } from 'reactjs-tiptap-editor';
import { FontSize, RichTextFontSize } from 'reactjs-tiptap-editor/fontsize';
import { TextStyle } from '@tiptap/extension-text-style';
import 'reactjs-tiptap-editor/style.css';

const extensions = [Document, Paragraph, Text, TextStyle, FontSize];

export default function FontSizeExample() {
  const editor = useEditor({
    extensions,
    content: '<p>Try this feature here.</p>',
    immediatelyRender: false,
  });

  if (!editor) return null;

  return (
    <RichTextProvider editor={editor}>
      <RichTextFontSize />
      <EditorContent editor={editor} />
    </RichTextProvider>
  );
}

How to use

Register TextStyle. Configure fontSizes with CSS sizes such as 14px or objects such as { name: "Large", value: "24px" }. Use editor.chain().focus().setFontSize("18px").run() or unsetFontSize() from your own controls.

Configuration

import { FontSize } from 'reactjs-tiptap-editor/fontsize';

FontSize.configure({
  fontSizes: ['Default', '14px', '18px', { name: 'Large', value: '24px' }],
});