---
title: "How long does DNS propagation take?"
date: "2014-10-28"
category: "dns"
slug: "how-long-does-dns-propagation-take"
---

DNS propagation typically takes between 15 minutes and 24 hours. In rare cases, it may take longer. Propagation begins once the [[nameserver-settings]] are changed through your domain registrar (the company where your domain name is registered).

## How TTL Affects Propagation

DNS maps a hostname (e.g. `example.com`) to an IP address (e.g. `64.22.68.1`). When a DNS server resolves this mapping, it returns the IP address along with a **TTL (time-to-live)** value -- the number of seconds that result is considered valid. TTL values typically range from 15 minutes to 24 hours.

Once the TTL expires, the resolver discards the cached result and fetches a fresh one. This is why DNS changes are not instant -- resolvers around the world hold onto the old result until their cached copy expires.

## Trade-Offs of Lower TTL Values

A lower TTL means resolvers refresh more frequently, reducing the delay when you change IP addresses. However, each DNS query adds 2-50 ms of overhead depending on network distance and congestion. This overhead is added to every page load.

For this reason, only reduce TTL below `43200` (12 hours) if you anticipate making DNS changes (such as a server migration) within the next 24-48 hours. Once the migration is complete, raise the TTL back to its default value.

## See Also

- [[dns-work]]
