What is DNS propagation?
DNS propagation is the time a change to a domain's DNS records takes to reach everyone, as resolvers around the world drop their cached copies of the old records.
In more detail
Nothing is actually pushed out. Every resolver that looked up your record keeps a copy for as long as its TTL (time to live) says, then asks again. Until each copy expires, some visitors still get the old answer.
Changing name servers takes longer than changing a single record, because the delegation is cached at the domain-extension level, commonly for up to two days.
Worked example
An A record has a TTL of 3,600 seconds. After you change it, a resolver that cached it just before the change keeps the old address for up to an hour. Lowering the TTL to 300 seconds a day ahead means the switch completes for everyone within about five minutes.
See also
Related terms: Downtime and TTFB (time to first byte). Free tool: DNS and HTTP headers. How OwlHound helps: Website uptime monitoring. All terms: monitoring glossary.
Frequently asked questions
How long does DNS propagation take?
As long as the old record's TTL, for record changes: often minutes to an hour. Name-server changes can take up to about 48 hours.
Can I speed it up?
Not after the change. Before it, lower the TTL and wait for the old TTL to pass; then the change itself spreads quickly.
Why do I see the new site but my colleague doesn't?
Your resolvers asked again sooner. Each network and device keeps its own cached copy until it expires.
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