Which of the following best defines 'fixity' in digital preservation?

'Fixity' in digital preservation fundamentally refers to the assurance that data has not been altered. This concept is crucial in the context of preserving digital materials, as it ensures the integrity and authenticity of digital objects over time. Fixity allows archivists and preservationists to monitor and confirm that files remain in their original state and have not been subjected to unauthorized changes or corruption.

This assurance of data integrity is often maintained through various methods, such as creating checksums or hash values for files when they are first created or ingested into a digital repository. By periodically recalculating these values and comparing them to the original, preservationists can confirm that the data is unchanged. This is vital for ensuring that digital records remain trustworthy and reliable for future use, particularly in legal, historical, or research contexts.

The other options do not accurately capture the essence of 'fixity.' For example, visual appeal does not pertain to the preservation of data integrity, accessibility is about the ease with which data can be retrieved and used, and authenticity verification is more about proving that the data is what it claims to be, which while related, is not the same as ensuring that the data remains unchanged.