Multiple Data Availability (MultiDA)

Multiple data availability, sometimes written MultiDA or multi-DA, refers to arrangements in which a rollup or other chain publishes the data behind its transactions to more than one data availability layer, rather than relying on a single one. Data availability means making sure the information needed to check and rebuild a chain's state is published and retrievable; rollups such as optimistic rollups and ZK-rollups traditionally post it to Ethereum, while specialised networks such as Celestia offer cheaper alternatives that use data availability sampling. Publishing to several layers aims to keep a chain working if one layer fails, is censored or becomes expensive, or lets a project choose by cost. The trade-offs are extra complexity and fees. The term is not formally standardised, and projects use it in slightly different ways.