Apps with 'Prototyping' feature

Pencil is a standalone app or Firefox extension* that lets you create diagrams or UI mockups. It doesn't have collaboration/multi-user features.

The collaborative interface design tool.

Online diagram and flowchart software that supports Microsoft Visio import and can work on any operating system.

Adobe XD (Experience Design) is a vector-based tool developed and published by Adobe Inc for designing and prototyping user experience for web and mobile apps.

to design circuits, as well as so called "layouts", be it PCB or stripboard or breadboard...
very-very handy a tool, very complex but very simple to use.

The digital product design platform powering the world’s best user experiences.

Build production-ready experiences without coding.WEBFLOW DESIGNERBring your design vision to life in clean, semantic HTML5, CSS, & JavaScript.CMS & E-COMMERCE

Scalable, secure, cross-device and enterprise-ready team collaboration tool for distributed teams. BETTER TEAMS, BUILDING BETTER THINGS

Create websites quickly and customize them with ease. Based on Bootstrap, HTML5 and SASS, Pingendo lets you create and manage webpages from prototyping to deploy.

The collaborative design platform. Wireframe, prototype, design online and create design specs in one place. Or create an integration with our API.

Framer combines the power of code with the ease of visual editing. Prototype beautiful microinteractions or realistic apps. It’s time to design with development in mind.

Origami Studio is a free design tool built by Facebook designers for creating interactive UI prototypes.

The most powerful way to plan, prototype, and hand off to developers, all without code.

Principle makes it easy to create animated and interactive user interface designs. Whether you're designing the flow of a multi-screen app, or new interactions and animations, Principle lets you create designs that look and feel amazing.

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.