CSS - Canvas
For all media, the term canvas describes “the space where the formatting structure is rendered.”
The canvas is infinite for each dimension of the space, but rendering generally occurs within a finite region of the canvas, established by the user agent according to the target medium.
For instance, user agents rendering to:
generally impose a minimum width
and choose an initial width based on the dimensions of the viewport
generally impose width and height constraints.
an aural medium
may impose limits in audio space, but not in time.
Documentation / Reference