What is DNS propagation, and why does a change take time?
The Domain Name System (DNS) is the internet’s address book. It turns a name like example.com into the numeric address of the server that hosts the site. When you change a record, the new answer does not appear everywhere at once. That delay is called DNS propagation.
Why it is not instant
DNS answers are cached on purpose, so the internet does not have to ask for the same thing millions of times. Your internet provider, your router and your own device all keep a copy. Each copy is kept for as long as the record’s TTL (time to live) allows.
So when you change a record, anyone who looked it up recently keeps seeing the old answer until their copy expires. Someone who has never visited sees the new one straight away. That is why a site can work for you and not for a friend.
How long does it take?
- With a short TTL of 300 seconds (five minutes), most places update within minutes.
- With a TTL of 3,600 seconds (one hour), expect up to an hour.
- With a TTL of 86,400 seconds (a day), expect up to a day.
- Changing the name servers of a domain is slower, because the registry has its own cache. It can take up to 24 to 48 hours.
Before you move a website
- A day or two before the move, lower the TTL on the records you will change to 300 seconds.
- Make the change at a quiet time.
- Keep the old server running until the new one is confirmed working.
- After everything is stable, raise the TTL again.
Seeing what the world sees
The checker shows the DNS records we find for a site (A, AAAA, CNAME, MX and name servers). Our regional probes also look the site up from other countries, so differences between places show up as failures in some regions and success in others.
If a site still does not load on your own device after the change has had time to spread, flush your DNS cache.
Is it down for everyone, or just you? Paste an address and we test it from fifteen places.
Open the checkerRelated guides
- How to flush your DNS cache on Windows, Mac and Linux
- What happens when a domain name expires?
- Why a website can be down for some people and not others
Last updated 2 November 2026. Written by the siteupdown.com team. Spotted a mistake?