The property of a data structure in computer science that data cannot be changed once it has been written. Append-only data structures like blockchains are immutable, they lack a delete operation that allows removal of data from the chain.

Immutability has been criticized as a vector for abuse and harassment when personally identifiable information cannot be removed from a publicly accessible system.

See also smart contracts and pseudonymous.


  1. White, Molly. 2022. ‘Abuse and Harassment on the Blockchain’. Molly White. 22 January 2022.
  2. White, Molly 2022. 'Abuse on the blockchain'. Guest lecture at Stanford University.
  3. Guadamuz, Andres. 2019. ‘All Watched over by Machines of Loving Grace: A Critical Look at Smart Contracts’. Computer Law and Security Review 35 (6): 105338.