The viewBox attribute defines the position and dimension, in user space, of an SVG viewport.
The value of the viewBox attribute is a list of four numbers: min-x, min-y, width and height. The numbers min-x and min-y represent the top left coordinates of the viewport. The numbers width and height represent its dimensions. These numbers, which are separated by whitespace and/or a comma, specify a rectangle in user space which is mapped to the bounds of the viewport established for the associated SVG element (not the browser viewport).
You can use this attribute with the following SVG elements:
<svgviewBox="0 0 100 100"xmlns="http://www.w3.org/2000/svg"><!--
with relative unit such as percentage, the visual size
of the square looks unchanged regardless of the viewBox
--><rectx="0"y="0"width="100%"height="100%"/><!--
with a large viewBox the circle looks small
as it is using user units for the r attribute:
4 resolved against 100 as set in the viewBox
--><circlecx="50%"cy="50%"r="4"fill="white"/></svg><svgviewBox="0 0 10 10"xmlns="http://www.w3.org/2000/svg"><!--
with relative unit such as percentage, the visual size
of the square looks unchanged regardless of the viewBox
--><rectx="0"y="0"width="100%"height="100%"/><!--
with a small viewBox the circle looks large
as it is using user units for the r attribute:
4 resolved against 10 as set in the viewBox
--><circlecx="50%"cy="50%"r="4"fill="white"/></svg><svgviewBox="-5 -5 10 10"xmlns="http://www.w3.org/2000/svg"><!--
The point of coordinate 0,0 is now in the center of the viewport,
and 100% is still resolve to a width or height of 10 user units so
the rectangle looks shifted to the bottom/right corner of the viewport
--><rectx="0"y="0"width="100%"height="100%"/><!--
With the point of coordinate 0,0 in the center of the viewport the
value 50% is resolve to 5 which means the center of the circle is
in the bottom/right corner of the viewport.
--><circlecx="50%"cy="50%"r="4"fill="white"/></svg>
The exact effect of this attribute is influenced by the preserveAspectRatio attribute.
Note: Values for width or height lower or equal to 0 disable rendering of the element.
marker
For <marker>, viewBox defines the position and dimension for the content of the <marker> element.