DNS Changes: Understand TTL and Plan a Safe Migration

DNS changes are not always visible everywhere at once. Resolvers cache answers according to TTL, and a resolver may continue returning an older record until its cache expires.

Before moving a website, inventory the A and AAAA records, CNAMEs, MX records, TXT records, and any service-specific records. Lowering TTL ahead of a planned migration can shorten the transition, but do it early enough for the old TTL to expire. Keep email records in the plan; moving a website does not automatically mean mail should move too.

Test the new server using a temporary hosts-file entry or another controlled method before changing public DNS. Confirm the site, certificate, redirects, and application dependencies work on the destination. When changing nameservers, remember that the authoritative zone itself must contain the required records.

After the change, query multiple resolvers and the authoritative nameservers. Avoid repeatedly editing records because one device still shows a cached answer. Maintain the old server for an appropriate overlap period and watch traffic, mail delivery, and error logs before decommissioning it.