R package peakRAM. When working with big datasets, RAM conservation is critically important. However, it is not always enough to just monitor the size of the objects created. So-called ”copy-on-modify” behavior, characteristic of R, means that some expressions or functions may require an unexpectedly large amount of RAM overhead. For example, replacing a single value in a matrix duplicates that matrix in the backend, making this task require twice as much RAM as that used by the matrix itself. This package makes it easy to monitor the total and peak RAM used so that developers can quickly identify and eliminate RAM hungry code.