The portion of the viewport that is currently visible is called the visual viewport. This can be smaller than the layout viewport, such as when the user has pinched-zoomed. The visual viewport is the visual portion of a screen excluding on-screen keyboards, areas outside of a pinch-zoom area, or any other on-screen artifact that doesn't scale with the dimensions of a page.
- Visual Viewport API
- Viewport on Wikipedia
- A tale of two viewports (Quirksmode)
- Viewport in the MDN Glossary
- Layout viewport in the MDN Glossary