Glossary · Domains, DNS, email and certificates
DNS propagation is the time it takes for a change to a DNS record to be seen everywhere. Nothing is pushed out: resolvers keep serving their cached copy of the old record until its TTL runs out, then ask again.
When you change a record at your DNS provider, the domain’s authoritative nameservers usually answer with the new value within seconds to minutes. Resolvers at ISPs, companies and public services such as 1.1.1.1 and 8.8.8.8 cached the old answer for as long as its TTL (time to live) allowed, so different users see the change at different times.
Plan a change by lowering the TTL a day ahead, to 300 seconds for example, making the change, then raising it again. Nameserver changes at the registrar take longer, since the parent zone’s NS records often have TTLs of up to two days.
During propagation some users reach the old server and some the new one, so keep both working until the old TTL has passed. Names that didn’t exist before can be cached as missing too (negative caching, RFC 2308).
Longest wait ≈ the old record’s TTL
Example: A record with a TTL of 3600 seconds can be served from cache for up to an hour after you change it.
Uptimecheck DNS monitors ask the domain’s own authoritative nameservers directly, so a change shows at the next check without a resolver cache in between. When the nameservers disagree, for example while a change spreads between them, the monitor page says so, and a new record set is alerted once two checks in a row have seen it.
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ReadAt most as long as the old record’s TTL: often 5 minutes to an hour for ordinary records, and up to 48 hours for nameserver changes at the registrar.
Not after the change; cached copies expire on their own schedule. Lower the TTL well before a planned change. Some public resolvers let you clear their cache for one name.
Your resolver, operating system or browser has the old answer cached. Ask the authoritative nameserver directly, for example with dig @ns1.example.com example.com, to see what is actually published.
Set up your first monitor in under a minute, or look around the live demo first.
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