Able Particle Tracker (APT) is advanced particle tracking software. Tracking objects in video sequences is a sophisticated problem and a variety of special solutions have been produced, but typically they are strongly dependent on the context of the particular experiment. APT is a general package for particle tracking that is appropriate both for tracking of nanometer sized proteins as well for tracking of huge objects, such as planet or stars and for everything in between (droplets, colloidal particles, biological cells, animals, humans, vehicles etc.) Able Particle Tracker is user friendly program and can be mastered in 5 minutes! The whole tracking process consists of a few simple steps: opening the first image of a sequence, selecting particles/criteria for tracking and then fully automated tracking of the particles in subsequent images. The results (particle trajectories) are written in a text file which can be imported into other programs (such as Excel, Origin, Matlab, IDL...) for further analysis. APT can track multiple particles at the same time. It is fast no matter whether you simultaneously track one or 5000 particles.