Bitrot

Bitrot, also called data rot, is a colloquial term for the gradual corruption of stored digital data over time. It can affect databases, documents, multimedia, and backups, even when hardware appears healthy. Bitrot is not a single failure mode but a spectrum of phenomena that can lead to unreadable or corrupted files and degraded data reliability.

Causes include physical degradation of storage media (magnetic disks, optical media, flash memory), latent errors in memory or on-disk formats, aging media, and environmental factors such as radiation or power events that induce bit flips. Silent data corruption can occur when checksums are absent or insufficient, so errors go unnoticed until access attempts fail. Software issues such as faulty compression, metadata corruption, or obsolescence of file formats can also contribute to what archivists describe as bit rot.

Detection and mitigation rely on data integrity measures: cryptographic or strong checksums, routine data scrubbing, and redundant storage with error detection (such as RAID and ZFS) and sometimes error-correcting memory. Regular backups, periodic migration to new media, verification against known-good hashes, and using stable, well-documented formats all reduce risk. Digital preservation often combines multiple strategies and geographically distributed copies to improve resilience.

Bitrot is a concern for long-term data archives, libraries, and scientific datasets, highlighting the need for proactive integrity controls rather than relying on a single backup. While decay rates vary, best practice is to assume occasional corruption and plan for frequent validation, refreshing, and redundancy.