Principle is a Mac-only, animation-focused prototyping tool, a driver-and-connections system where properties respond to interaction (drag, scroll, tap) with precisely timed spring animations, built for communicating complex UI transitions to engineering.
$129 one-time (macOS software + 1 year of updates), then usable forever; optional update renewal at $99/year.
Designers needing to communicate sophisticated, physics-based animation and interaction behavior clearly to engineers: one-time-purchase model over a subscription.
The one-time purchase (with optional paid update renewal) is a real differentiator from subscription-based competitors, worth it specifically if the team prefers to avoid recurring costs and doesn't need every future update immediately.
Design animated, interactive user interfaces without writing code.
