PIT vs Stryker: licensing, GitHub activity, and what each is actually for. Neutral comparison, no paid rankings.
PIT: Open source. 1,874 GitHub stars. State-of-the-art mutation testing system for Java and JVM. Provides mutation coverage metrics.
Stryker: Open source. 3,203 GitHub stars. Mutation testing framework for JavaScript and TypeScript. Tests your tests by introducing bugs and checking if tests catch them.