Why does my Bitcoin address keep changing?
Why does my Bitcoin address keep changing?
See also: Address reuse
Unlike postal and email addresses, Bitcoin addresses are designed to be used exactly once only, for a single transaction. Originally, wallets would display only a single address at a time, and change it when a transaction was received, but an increasing number of wallet implementations now generate an address when you explicitly want to receive a payment.
While it is technically possible to use an address for an arbitrary number of payments, this works by accident and harms both yourself and other unrelated third parties, so it is considered a bad practice. The most important concerns with such misuse involve loss of privacy and security: both can be put into jeopardy when addresses are used for more than a single transaction only.