Great question! Let's break this down clearly—there's a crucial difference between what lives on the actual Bitcoin blockchain and what third-party tools (like blockchain explorers) display to you.

• Coinbase pre-generates batches of addresses
  Platforms like Coinbase don't create a brand-new address from scratch every time you request one. Instead, they generate a large pool of address-key pairs (public key + private key) in advance. When you ask for a receiving address, they just hand you an unused one from this pre-made pool. These addresses are part of Coinbase's wallet infrastructure, even if they’ve never touched a transaction.

• Third-party tools index more than just on-chain transactions
  The core Bitcoin blockchain only stores transaction data—there’s no entry for an address that’s never sent or received funds. But blockchain explorers and address trackers don’t just pull raw data from the chain. Many actively crawl and index addresses from major custodial platforms like Coinbase. They might get these addresses directly from the platform’s systems, or derive them from public keys Coinbase holds (since a Bitcoin address is just a hashed version of a public key).

• Unused addresses have no real on-chain record
  To be crystal clear: if your address has never been involved in any transaction, there’s zero mention of it in the actual Bitcoin ledger. The only reason you can "look it up" is because a third-party tool added it to their own database. If you queried a raw Bitcoin node (not a commercial explorer), it would return no data for that address—since there’s no transaction history tied to it.

In short: The address isn’t present on the blockchain itself until it’s used in a transaction. Its searchability comes from third-party services that pre-index custodial platform address pools.

内容的提问来源于stack exchange，提问作者Daniel D.