DNS maps domain names to host addresses. When buying or migrating hosting, many “site still won’t open” cases come from records not updated yet, wrong targets, or email records changed by accident. Common concepts below.
What A and CNAME do
An A record usually points the apex (e.g. example.com) to the host’s IPv4; a CNAME often aliases a subdomain (e.g. www) to another hostname. Exact values follow your hosting panel — after activating Shared Hosting or VPS, the provider usually gives the address or hostname to set.
Before editing records, confirm whether you change DNS at the registrar or switch to the host’s nameservers. The flows differ — mixing them often edits the wrong place.
TTL and expectations during cutover
TTL (Time To Live) is how long resolvers may cache a result. Before cutover, some people shorten TTL so later changes propagate faster; ISP and intermediate caches still vary, so do not treat any hour count as a guaranteed propagation time。
If some regions still see the old site after cutover, caches often have not expired. Compare old/new IPs, flush local DNS cache, and avoid flipping records repeatedly before you verify.
Do not ignore email and HTTPS at cutover
When changing only site A/CNAME records, avoid deleting MX or other mail-related records by mistake. If mail moves too, schedule it separately and verify receiving first.
After DNS points to the new host, confirm the SSL certificate covers the domain so browsers show HTTPS correctly. To compare plans or have someone check records, start from the contact page and leave your domain plus current host type.