The primary characteristic of a blockchain ledger is its immutability; once data is recorded, it cannot be altered or deleted. This feature ensures the integrity and trustworthiness of transaction records, making blockchain technology highly secure. Every transaction is linked in a chronological chain, creating a transparent and auditable history. This immutability inherently reduces the risk of fraud and increases confidence among users, as any attempt to modify past records would be evident to all participants in the network. Trust is established through inherent transparency.