As a specific version released in 2011 (CS5.1 was a minor update to CS5), is now legacy software. However, its notable features at the time included:

Before the "Creative Cloud" (CC) reigned supreme, Adobe operated on the "Creative Suite" (CS) model. CS5 was the fifth major iteration, and the was significant. Adobe Illustrator CS5.1 was primarily an optimization and cloud-integration patch.

Dedicated windows for managing layers, colors (Swatches), and object properties. Key Features Introduced in CS5/5.1

Before CS5.1, drawing in 3D perspective was a painful manual process involving vanishing points drawn with pencil tools. CS5 introduced the , and CS5.1 refined its stability.

: A more intuitive alternative to the Pathfinder panel, this tool lets you merge, subtract, and fill overlapping areas of shapes simply by clicking and dragging across them.