Inkscape. The most well-known free Illustrator alternative is the open-source Inkscape. It's available for Windows, Mac, and Linux. You can open AI files directly in Inkscape.
What programs can open Illustrator files?
Adobe Illustrator is a professional drawing and design application, and saves drawings in a vector graphic format with the . ai file extension. Though you can open this type of file in almost any Adobe application -- including Photoshop, InDesign, Acrobat and Flash -- the . ai file type is native to Adobe Illustrator.
Can you open a Mac Illustrator file on a PC?
Yes. Unless the the Mac version of illustrator is same or higher.