Zooming (in or out) is just temporarily magnifying your view on the drawing so you can examine the small details (when zoomed in) or look at the whole picture (when zoomed out). Zooming does not change the drawing itself, just your view on it.
The (almost) infinite scalability of vector graphics makes zooming one of the most common operations in vector work. It’s not surprising that Inkscape offers a lot of different ways to zoom.
First of all, the current zoom level is always displayed in the lower right corner of your editing window, in the Z: editable field, as shown in Figure 3-9. You can always click there, type the desired level of zoom, and press 
.
The simplest way to zoom in or out using the keyboard is by pressing the plus sign and minus sign keys (
and 
), correspondingly. The keys on the keypad (on the rightmost end of the keyboard on most desktop computers) work just as well as those in the main keyboard (above the letter keys). Moreover, the equal sign (
), usually located on the same physical key as the plus sign, also works for zooming in, and the underscore (
), usually on the same key as the minus sign, works for zooming out; in other words, you never have to press 
to access the zooming keys.
Zooming by using the plus and minus keys works in all tools and modes, except when you are editing text. In text, the plus and minus keys on the main keyboard insert the corresponding characters, but the keypad and keys still work for zooming.
Often, your hand is on your mouse or tablet pen, and reaching for the keyboard is inconvenient. The simplest way to zoom in by mouse is by pressing the middle button (on many mice, this is not actually a button but a scroll-wheel that you can click as well as rotate). The point you click will keep its relative position in the window after the zoom, so by clicking some small object, you zoom into that object—unlike the plus sign and minus sign key zoom, which zooms into the center of the visible area. To zoom out, middle-click with the key pressed.
Additionally, with a scrollwheel mouse, you can rotate the wheel up to zoom in or down to zoom out. By default, you need to press 
for that, because the scroll wheel without modifiers scrolls the document, as in most other programs. There’s an option, however, to make it zoom without modifiers and scroll with ; it is set in the Scrolling page of the Inkscape Preferences dialog.
You can adjust the amount of zooming in or out that the plus and minus sign keys, the middle click, and the single scrollwheel click perform. This value is set in the Steps tab of the Inkscape Preferences dialog. The default is 141 percent, which is 100 percent multiplied by the approximate square root of two, so that two subsequent zoom-in keystrokes zoom you in exactly 200 percent.