Depending on the editing operations you want to perform, you may want to view the entire file or only a small section. You can change the magnification of each file independently.
Control-click the waveform, choose Zoom > Time > from the context menu, and then choose a command from the submenu to zoom quickly.
To zoom in and out in time by small increments, press the Up Arrow/Down Arrow keys.
Choose View > Zoom Time > In Full to maximize the horizontal magnification to 24:1 (24 pixels per sample).
Choose View > Zoom Time > Out Full (or press Ctrl+Down Arrow) to zoom out to the lowest magnification so that the entire sound file will fit on the screen.
If you're using a trackpad, you can use gestures to zoom:
Hold Shift and pinch to zoom.
Hold Option+Shift and pinch to zoom incrementally.
Swipe up or down with two fingers to zoom.
Hold Option and swipe up or down with two fingers to zoom incrementally.
Choose View > Zoom Time > Selection to maximize the time selection to fit the width of the editor.
When the Event Mode button is selected, choose View > Zoom Time > Event to maximize the selected event to fit the width of the editor.
Control-click the waveform, choose Zoom > Level > from the context menu, and then choose a command from the submenu to zoom quickly.
To zoom in and out vertically by small increments, press Shift+Up Arrow/Down Arrow.
Choose View > Zoom Level > Entire Waveform to allow viewing of the entire amplitude range.
Choose View > Zoom Level > Visible Waveform to allow viewing of the amplitude range in the visible portion of the editor.
Choose View > Zoom Level > Selected Waveform to allow viewing of the current selection's amplitude range.
If you're using a trackpad, you can pinch to zoom vertically.