Block validity refers to the criteria that a new block must meet before it can be added to the blockchain. This involves ensuring that all transactions within the block are legitimate, correctly formatted, and adhere to the network’s rules. Key aspects of block validity include verifying that transactions are properly signed by the sender’s private key and that the sender has sufficient balance to cover the transaction.

Additionally, the block itself must be structured correctly and include the required metadata, such as timestamps and references to previous blocks. When miners or validators create a new block, they perform these checks. If a block is deemed valid, it is propagated through the network and added to the chain.

If not, it is rejected. Maintaining block validity helps to prevent fraud, double-spending, and ensures the integrity and security of the entire blockchain system.