Immutable

Immutability in blockchain means that once data is written to the blockchain, it cannot be changed or deleted. This is ensured by each block containing a cryptographic hash of the previous block, linking them in an unalterable chain.
Any attempt to modify a block would require re-mining all subsequent blocks, which is computationally infeasible in large, secure networks. Consensus mechanisms like Proof of Work or Proof of Stake further safeguard this immutability by requiring network agreement for changes, making malicious alterations extremely difficult.
This property makes blockchain ideal for applications where data integrity and historical accuracy are paramount, like financial transactions, proof of authenticity, or record-keeping.