DOMAIN LIFECYCLE
What happens when a domain expires?
The website files may still exist on the server, but the address that points people to them can stop working. Domain expiry can also affect email and other services using the same domain.
Contact the registrar immediately
ICANN's current guidance says that if a domain has expired you should contact the registrar or reseller for the available renewal options. Different registrars can handle the immediate post-expiry period differently. See ICANN's expired-domain guidance.
Some domains enter a redemption period
For applicable generic top-level domains, ICANN documents a 30-day Redemption Grace Period after deletion where the domain can still be restored through the registrar, usually at additional cost. See ICANN redemption guidance.
After deletion, someone else may register it
If the domain is not renewed or restored in time, it can eventually return to general availability. At that point you can lose the name entirely.
Auto-renew helps, but check the payment method
Auto-renew is useful only if the registrar account and payment method are current and renewal notices reach an address you still monitor.
Keep domain ownership separate from the website supplier where practical
If a designer or agency controls the registrar account in its own name, leaving that supplier can become much harder. Make sure the registrant and account ownership are clear.
Treat the domain as a critical credential
Use a strong account password, multi-factor authentication and renewal reminders. Losing control of the domain can disconnect several services at once.