Figma
Figma is a collaborative product-design platform for turning ideas into interfaces, prototypes and implementation-ready assets. Its shared workspace lets designers, engineers and stakeholders work on the same evolving material rather than exchange static files.
Penpot
Penpot is an open-source browser-based design and prototyping platform that connects visual design with the standards developers use.
Subframe
Subframe combines interface design, a coding agent and an integrated browser in one workspace. It is aimed at people building web products who want visual control without separating mockups from the code that will actually ship.