Penpot

Penpot is the open source design tool that's gaining real traction as a Figma alternative. It runs in the browser with real-time collaboration, uses SVG as its native format (which means design-to-code handoff is genuinely clean), and includes every feature you need for UI design and prototyping. The biggest selling point is the pricing: there's no per-editor fee, no premium tier locking features, no surprise bills at the end of the month. Self-hosting it means complete data control. What makes Penpot interesting is how it approaches design differently from Figma — the flex layout system is more web-native, which means designs translate to actual HTML more naturally. It's not as mature as Figma yet, and some power users will miss advanced features. But for most UI design tasks, it's more than capable, and the open source foundation means it can only get better.

Good first choice if you want a practical tool without spending the afternoon reading developer docs.