How DNS caching decides what you see

When you type a name into a browser, the answer usually comes from a cache, not from the authoritative server. Your browser, your operating system, your router and your provider's resolver can each keep a copy of the answer for as long as its TTL (time to live) allows.

This is why a DNS change can look instant on one device and take hours on another. If you plan a change, lower the TTL a day in advance and raise it again afterwards. To clear the local cache, use ipconfig /flushdns on Windows or resolvectl flush-caches on a Linux system running systemd-resolved.