When creating or editing a vector graphic in Adobe Illustrator, you work in the colour preview mode by default. However, all that colour can get in the way when making precise adjustments in detailed illustrations. Illustrator offers an outline preview mode, sometimes referred to as a wireframe preview, which allows you see your work in paths or lines only without the fill colours obscuring details behind the shapes.
Go to the "View" menu at the top of the screen and select "Outline" to view the entire image in outlines. Return to the colour preview mode by going to "View" and selecting "Preview." You can also toggle between the outline and preview modes using the keyboard shortcut "Ctrl+Y" on a Windows PC or "Command+Y" on a Mac.
Go to the Layers panel and hold the "Ctrl" or "Command" button while clicking the eye icon next to a layer. This will display only the selected layer in outline mode and all other layers will remain in colour. Hold the "Ctrl" or "Command" button and click the eye icon again to return the layer to colour preview mode.
Hold the "Alt" and "Ctrl" or "Option" and "Command" buttons and click the eye icon next to a layer in the Layers panel to view all unselected layers in outline mode. The layer you clicked will remain in colour preview mode. Repeat to return unselected layers to colour preview mode.
By default, linked images and raster elements display as outlined boxes with an "X" inside when in outline preview mode. To see these images in outline mode, go to "File" and select "Document Setup." In the resulting dialogue box, select "Show Images In Outline Mode."