Fixity, the property of a digital file or object being fixed or unchanged, is a cornerstone of digital preservation. Fixity information, from simple file counts or file size values to more precise checksums and cryptographic hashes, is data used to verify whether an object has been altered or degraded.
Many in the preservation community know they should be establishing and checking the fixity of their content, but less understood is how, when and how often? The National Digital Stewardship Alliance Standards and Practices and Infrastructure working groups have published Checking Your Digital Content: What is Fixity and When Should I Be Checking It? (PDF) to help stewards of digital objects answer these questions in a way that makes sense for their organization based on their needs and resources.