“Propagation” is the time between changing a DNS record and everyone seeing the new value. Nothing is actually being pushed around the internet. Resolvers everywhere are holding cached copies of the old answer, and each one lets go when its copy expires.
Most record changes are visible everywhere within the record’s TTL, often 1 hour and at most a day or two. Changing nameservers can take up to 48 hours, because the .com (or other) servers’ NS records have long TTLs of their own.
Why it varies
- The old TTL decides the wait. If the record had a TTL of 86400 seconds (24 hours), a resolver that fetched it just before your change keeps the old answer for up to a day.
- Resolvers fetched at different times. That is why your colleague sees the new site while you still see the old one.
- Your own devices cache too. Your computer and browser keep answers for a short while. Flushing your DNS cache clears them.
Nameserver changes take longer
Changing a record at your current DNS host is controlled by that record’s TTL. Changing nameservers, for example moving DNS from your registrar to Cloudflare, is different. The registry for the domain’s ending, such as .com, publishes your nameservers with its own TTL, and for .com that is 172,800 seconds: 48 hours. Resolvers that cached the old nameservers keep asking them until that runs out.
In practice most resolvers pick up the change within a few hours, but plan for two days. During that time some visitors are answered by the old DNS host and some by the new, so:
- Copy every record to the new DNS host before switching nameservers, so both give the same answers.
- Do not cancel the old DNS host or delete its records until at least 48 hours after the switch.
- Do not change nameservers and the website’s server at the same time. Change one, let it settle, then change the other.
“Does not exist” is cached too
If someone looked up a name before you created it, their resolver cached the “no such name” answer. How long it keeps that is set by your zone’s SOA record, usually a few minutes to an hour. That is why a brand-new subdomain can work for you but fail for a colleague who tried it a minute too early.
Timeline for common changes
| Change | Typical wait |
|---|---|
| Edit an A, CNAME or MX record with a 300-second TTL | About 5 minutes |
| Edit a record with a 3600-second TTL | Up to 1 hour |
| Edit a record with an 86400-second TTL | Up to 1 day |
| Add a brand-new record that was never looked up | Almost immediate |
Change nameservers on a .com domain | A few hours, up to 48 |
| Register a new domain | Minutes to a few hours |
Check what the world sees
Ask public resolvers directly, which skips your own caches:
dig example.com A @1.1.1.1 +short
dig example.com A @8.8.8.8 +short
dig example.com A +noall +answerThe last line shows the TTL counting down on your resolver’s cached copy, which tells you how long until it refreshes. Web-based “propagation checker” tools run the same query from many countries at once.
Why it works on one device and not another
Each device and network can be using a different resolver with a different cached answer. Your phone on mobile data uses the carrier’s resolver, your laptop at home uses your provider’s, and your office may use its own. It is normal for them to disagree for up to one TTL. If one device keeps showing the old answer long after the TTL has passed, flush its cache: see how to flush your DNS cache.
A small number of resolvers keep answers longer than the TTL allows. You cannot fix those, which is another reason to keep the old server running for a day or two after a move.
Make the next change fast
- A day or more before the change, lower the record’s TTL to 300 seconds (5 minutes).
- Wait at least as long as the old TTL, so every cached copy is the short-lived one.
- Make the change. Now the world catches up within about five minutes.
- Afterwards, raise the TTL back to something like 3600.
This is the core of changing hosts without downtime.
Related
Something out of date? Software changes. If a step no longer works, tell us and we will check it and update the page.
