How to Check DNS Propagation

“I changed my DNS, but it still shows the old value.” The cause is usually caching. Here are the steps to find out how far your change has spread.

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“Propagation” is really caching

When you change a DNS setting, the name servers that manage your domain (the authoritative DNS) are updated immediately. The delay comes from DNS servers such as Google’s or your ISP’s, which remember the previous answer for as many seconds as the TTL says. It isn’t that the change travels around the world one place at a time. Each cache is simply waiting for its entry to expire.

Steps to narrow it down

Check the authoritative DNS: Choose “Authoritative” as the server to ask. If it still shows the old value, your change hasn’t been saved yet, or you are looking at a different name server.
Compare with public DNS: Select Google, Cloudflare and Quad9 at the same time. If the authoritative DNS is new and the public DNS is old, you are just waiting for the cache to expire.
Look at the TTL: The TTL in the result is a guide to how many more seconds the value will stay cached. If the value from public DNS keeps counting down, the cache is still there.
Clear your own computer’s cache: If public DNS is up to date but only your own environment shows the old value, the cause is your device’s cache.

Clearing your device’s DNS cache

# Windows
ipconfig /flushdns

# Mac
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Cases where it takes longer

When you change name servers (NS): The NS information at the parent level (such as .jp or .com) is cached, so it can take up to 24 to 48 hours.
When you looked up a nonexistent name first: The “does not exist” result (NXDOMAIN) is also remembered for a while, depending on the value in the SOA record.
When the TTL before the change was long: With 3600 (1 hour) or 86400 (1 day), the old value stays for that long. The standard practice is to shorten the TTL before a migration.

The record types to check are A, AAAA and CNAME for websites, and MX for email.

FAQ

How long does DNS propagation take?

For a record change, the TTL before the change is a good guide. For a name server change, it can take up to 24 to 48 hours.

Why do the authoritative DNS and public DNS show different results?

Public DNS servers cache the previous answer. Once the TTL expires, they switch to the new value.

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Last updated: 2026-10-21