What are some alternatives?
When comparing Zeplin and Invision, you can also consider the following products
Framer - Bring your designs to life.
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
Webflow - Build dynamic, responsive websites in your browser. Launch with a click. Or export your squeaky-clean code to host wherever you'd like. Discover the professional website builder made for designers.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.