Every time a new block is added to the blockchain, all nodes on the network must download and verify the new block. In order to do this, they need to have a complete copy of the blockchain, which can be quite large.
Other related questions:
Q: Do you download a blockchain?
A: No, the blockchain is downloaded automatically by the bitcoin software.
Q: How often does the blockchain update?
A: The blockchain is updated every 10 minutes on average.
Q: Do I need to download the entire blockchain to mine?
A: No, you do not need to download the entire blockchain to mine. However, you will need to have a full copy of the blockchain in order to verify and validate transactions.
Q: How long does it take to download entire blockchain?
A: It can take up to a week or more to download the entire blockchain.