A method for monitoring the free space of a stack of a microcontroller during the execution of a process using spaces of the stack from a start address to an end address of the stack, in which the method includes: in a prior step, writing N keys in the stack at N addresses of the stack, the memory space between two consecutive keys decreasing in a direction from the start address to the end address of the stack; and, in a step of executing the process, saving the address of the current key, corresponding to the address of the existing key, among the N keys, that is closest to the stack start address.