UX-App is described as 'Mock with real html components, prototype with draggable puzzle pieces & share in any browser. Collaborate through threaded comments per component + full group chat' and is an app in the Development category. There are six alternatives to UX-App for Mac, Windows, Online / Web-based, Linux and Sketch. The best alternative is Axure RP. It's not free, so if you're looking for a free alternative, you could try Moqups. Other great apps like UX-App are Mockplus (Paid), UXPin (Paid), HotGloo (Paid) and Pidoco (Paid).
Mockplus is a desktop-based prototyping tool. It can be used to create wireframes/mockups/prototypes for any mobile and web apps with ease. This tool will make UI/UX designers prototype faster, smarter and easier.
UXPin is a web-based system for managing design documents like wireframes, sitemaps, persona descriptions or flowcharts. It lets you upload image files, invite teammates to review and comment on them, and keep track of revisions.
HotGloo is a UX, wireframe and prototyping tool designed to build wireframes for web, mobile and wearables. Create and share fully interactive prototypes with your team and clients and gather feedback on the process.