Mockingbird : Mockingbird is an online tool that makes it easy for you to create, link together, preview, and share mockups of your website or application.
Figproxy : Figproxy is a tool that enables rapid prototyping of tangible user experiences allowing Figma prototypes to talk to the external world.
More specifica...
Pencil Project : Pencil is built for the purpose of providing a free and open-source GUI prototyping tool that people can easily install and use to create mockups in p...
iPlotz : Wireframing, mockups and prototyping for websites and applications
Origami is a free tool for designing modern user interfaces.
