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DNS Propagation and TTL, Fully Explained

See step by step why a DNS record change doesn't take effect right away.

What DNS propagation is

It refers to the time it takes for a change to a domain's DNS records (such as an A or CNAME record) to be reflected across DNS servers and user devices around the world.

The role of TTL

Every DNS record has a TTL (Time To Live) set in seconds. TTL specifies how long a resolver is allowed to keep an answer cached before checking again, and until that TTL expires, a resolver keeps returning the stored value instead of looking it up fresh.

Why multiple layers of caching cause the delay

Your ISP's recursive resolver, your operating system, and your browser each cache DNS responses independently. If even one of those layers still holds an unexpired TTL for the old value, that layer will keep showing the old answer for a while even after the record itself has changed.

What affects propagation time

The TTL that was set on the record before the change, each user's resolver having its own caching policy, and how quickly the domain registrar or nameservers actually apply the change all combine to affect real-world propagation time.

Lower the TTL ahead of time

Before an important DNS change, such as a server migration, it's a good idea to lower the TTL to something short, like 300 seconds, a day or two in advance. Making the change only after the old, longer TTL has fully expired from caches lets the new value propagate much faster.

How to check propagation status

An online DNS checker that queries DNS responses from multiple locations around the world simultaneously lets you see how the change has (or hasn't) rolled out region by region. If your own computer still shows the old value, it's also worth flushing your local DNS cache.

If you want to clear the DNS cache on your own device

If you're wondering how to manually clear old DNS data cached on your own computer or browser, look into how to flush your local DNS cache β€” it's often the fastest fix when everywhere else has already updated but your device hasn't.

If you want the full DNS lookup picture

If you're curious about the complete process of how a domain name gets translated into an actual IP address in the first place, it's worth reading a full walkthrough of how DNS resolution works alongside this page.

Frequently Asked Questions

How long does DNS propagation usually take?

There's no fixed time. If the TTL was lowered ahead of time, most changes are reflected within minutes to a few hours, but if the previous TTL was set long, or a particular resolver holds onto its cached value longer than expected, it can take more than a day.

My computer keeps connecting to the old site. Why?

Even if the change has already propagated everywhere else, your computer or browser will keep using the old value as long as a cached entry with an unexpired TTL is still sitting there. Manually clearing your local DNS cache almost always resolves this immediately.