What are some alternatives?
When comparing UsabilitySquare and UXtweak, you can also consider the following products
UX Flow Wireframe Prototyping System - Create beautiful user flows prototypes for your next project
UsabilityTools - Where UX meets Conversion. Unlock the Potential Behind Remote Research and Testing
ProtoPie - ProtoPie is the easiest tool used to turn your UI/UX design ideas into highly interactive prototypes for mobile, desktop, web, all the way to IoT.
Usability Testing Exchange - Free usability testing of, and feedback about, your website/app.
Usabilla - Collect user feedback and improve your websites, apps and emails with Usabilla's Voice of Customer Solutions.
Marvel User Testing - Record what users do with your designs and sketches. Free!