The best alternatives to SideIt are UX Tools, UI Oh My, and LightTable SX. If these 3 options don't work for you, we've listed a few more alternatives below.
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UX Tools is the easiest way to alleviate your tools anxiety by comparing the industry's best UX tools side by side. When was the last time you heard someone ask, "Which is best: InVision, Framer, or Marvel?" Send them a link to uxtools.co and let them decide for themselves.
LightTable SX lets you create an unlimited virtual canvas to layout, inspect and compare images while exploring the relationships between items. The canvas can be printed, exported and shared with other applications and internet services.
Want the iPhone 13 Mini but not sure if its too small? Compare My iPhone is a webpage that lets you see how big or small another iPhone is compared to your current iPhone. Includes a functioning keyboard that scales with the model you're comparing.