GeoGebra
Free dynamic math software for geometry, algebra, and calculus
Free
Learning Tools
Users draw geometric objects, define functions, and drag points to see relationships change. It includes graphing, spreadsheet, and 3D tools. A large library of shared activities covers school topics.
It runs in a browser and on phones and tablets.
Desmos is a close alternative for graphing. GeoGebra suits mathematicians and teachers who explore ideas visually.