# Immutability
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](blockchain.md) 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](smart-contracts.md) and [pseudonymous](pseudonymous.md).

## References
1. White, Molly. 2022. ‘Abuse and Harassment on the Blockchain’. Molly White. 22 January 2022. https://blog.mollywhite.net/abuse-and-harassment-on-the-blockchain/.
1. White, Molly 2022. 'Abuse on the blockchain'. Guest lecture at Stanford University. https://www.youtube.com/watch?v=hXBZ-BXfCSY
1. 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. https://doi.org/10.1016/j.clsr.2019.105338.