Desmos: Known for its premier free graphing calculator and a library of interactive digital activities where teachers can monitor student work in real-time.

GeoGebra: A dynamic platform featuring interactive tools for geometry, algebra, statistics, and 3D calculus, including a large database of community-created resources.

Mathigon (Polypad): Offers "The Mathematical Playground" with highly versatile virtual manipulatives—like fraction bars and geometry nets—to support deep conceptual exploration.

Mathsbot: A free hub for teachers featuring question generators, digital manipulatives, and worksheet creators that require no login.