Digital data consists of a fixed sequence of bits that are stored on data carriers. This sequence is called a bitstream. Since the lifetime and reliability of storage media is limited, individual bits may no longer be read correctly after longer time periods. This leads to loss of information. Bitstream preservation uses technical measures such as checksums and redundancy to ensure that the Bitstream remains unchanged over time and after changes in technology. It is a basic prerequisite for digital long-term preservation.