Zeplin

Penpot

Penpot is a web‑based, open‑source design and prototyping tool that lets UI/UX designers create wireframes, mockups, and interactive prototypes. It offers a collaborative environment similar to commercial alternatives while keeping data under your control. Because it is open source, teams can self‑host Penpot on their own infrastructure or use the free cloud offering, making it a flexible choice for freelancers, startups, and enterprises that need cost‑effective design workflows.

UXPin

UXPin is a UX/UI design and prototyping tool that lets teams build interfaces using real, code-backed components instead of static shapes, bridging the gap between design and development. It includes built-in React component libraries like MUI, Tailwind UI, and Ant Design, an AI Component Creator, and Git and Storybook integrations for syncing custom design systems.

Marvel

Marvel is a design platform that lets teams wireframe, design, and prototype digital products, then test them with real users and hand them off to developers. It is used by organizations ranging from startups to Fortune 100 companies, and includes Ballpark, a companion tool for running user research and surveys against Figma prototypes.

Mockplus

Mockplus is a UI/UX prototyping platform that lets designers build interactive prototypes with drag-and-drop interactions, animations, and mobile gestures without writing code. It ships with component libraries for iOS, macOS, Android, Web, and Material Design, plus centralized asset management for colors, fonts, and reusable components across a team. Teams work together with real-time co-editing, and finished designs can be imported from Axure or Adobe XD to migrate existing work. For handoff, Mockplus automatically generates specs, redlines, and CSS code snippets for developers, and an offline desktop edition (Mockplus 3) supports secure work when an internet connection isn't available.