Caliu supports the classic inline styles, and they all stay plain markdown underneath:
**bold** *italic* ~~strikethrough~~ `inline code`
You can type the syntax directly, use Cmd/Ctrl+B for bold and Cmd/Ctrl+I for italic, or reach for the toolbar.
The style bar (web app)
In the web app, the style bar sits at the bottom of the editor with buttons for every style, plus headings, lists, highlights, links, and more. On phones it floats above the keyboard while you type. You can show or hide it from the note's menu, or with Cmd/Ctrl+Shift+Y.
The formatting toolbar (iPhone, iPad, and Mac)
The native apps show a formatting toolbar too: above the keyboard on iPhone and iPad, and as a floating bar at the bottom of the editor on the Mac. Buttons light up to reflect the formatting at your cursor.
The native toolbar is also customizable. Open Edit Toolbar from the toolbar's More menu to choose which buttons appear up front and which stay tucked away in the menu.