How DNS Propagation Works

What is DNS Propagation?

DNS propagation is the process by which updated DNS records spread across all DNS servers worldwide. When you make a change to your DNS settings, that change doesn't instantly appear everywhere. Instead, it gradually propagates through the global network of DNS servers.

This process can take anywhere from a few minutes to 48 hours or more, depending on various factors. Understanding how propagation works helps you plan DNS changes and troubleshoot issues when things don't seem to update.

The Propagation Process

1. Update Made

You change a record on your authoritative nameserver

2. Caches Expire

DNS resolvers wait for their cached records to expire

3. New Data Fetched

Resolvers query your nameserver and cache the new records

Why DNS Propagation Takes Time

DNS Caching

The primary reason for propagation delays is caching. Every level of the DNS hierarchy caches records to improve performance and reduce load:

Browser cache: Your browser stores DNS lookups locally
Operating system cache: Your computer maintains a DNS cache
Recursive resolver cache: Your ISP or DNS provider caches responses
Intermediate caches: Enterprise networks and CDNs may cache DNS

Each cache holds onto records until their TTL (Time to Live) expires, regardless of whether the authoritative record has changed.

TTL (Time to Live)

Every DNS record has a TTL value that specifies how long (in seconds) the record should be cached. Common TTL values include:

300 seconds (5 minutes): Good for records that change frequently
3600 seconds (1 hour): Standard for most records
86400 seconds (24 hours): Common for stable records like NS

When you make a DNS change, servers that already have the old record cached will continue using it until the TTL expires.

Geographic Distribution

DNS servers are distributed globally. A change might appear in one location while still showing the old value elsewhere. This happens because:

Different resolvers cached the record at different times
Some resolvers may not respect TTL exactly
Network routing can affect which resolver serves a query

Factors Affecting Propagation Time

Previous TTL Value

The TTL of the old record determines the maximum time before caches expire. If your old TTL was 86400 (24 hours), propagation could take up to 24 hours.

ISP Caching Behavior

Some ISPs ignore low TTL values and cache records longer than specified. This is usually to reduce their DNS query load.

DNS Provider Performance

Slow or overloaded nameservers can delay the response to queries, extending propagation time.

Record Type

NS record changes typically take longer because they have higher TTLs and affect the fundamental zone delegation.

How to Minimize Propagation Time

Lower TTL Before Making Changes

The most effective way to speed up propagation is to reduce your TTL before making the actual change:

Lower the TTL to 300 seconds (5 minutes) at least 24-48 hours before your planned change
Wait for the old TTL period to pass so all caches pick up the new TTL
Make your DNS change
After confirming the change propagated, restore the TTL to normal

This technique ensures that when you make your change, caches will expire within minutes rather than hours.

Use a Reliable DNS Provider

Fast, reliable DNS providers ensure your authoritative servers respond quickly when resolvers query them. Popular options include:

Cloudflare DNS
AWS Route 53
Google Cloud DNS
NS1
DNSimple

Flush Your Local Cache

To see changes immediately on your own computer, you can flush your local DNS cache:

macOS:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Windows:

ipconfig /flushdns

Linux:

sudo systemd-resolve --flush-caches

Checking Propagation Status

You can monitor the progress of DNS propagation using tools that query DNS servers in different locations around the world:

Check DNS Propagation DNS Lookup Tool

Our propagation checker queries DNS servers in multiple countries and shows you where your changes have taken effect and where they're still pending.

Common Propagation Scenarios

Migrating to a New Web Host

When moving your website to a new server, you'll update the A record to point to the new IP address. During propagation:

Some visitors will see the old site
Some visitors will see the new site
This split can last until all caches update

Tip: Keep your old server running until propagation completes. Consider using a "site under maintenance" page on the old server to avoid confusion.

Changing Nameservers

NS record changes are the slowest to propagate because they affect the fundamental zone delegation. Plan for up to 48 hours and:

Set up all records on the new nameserver before switching
Keep records on both old and new nameservers during transition
Don't delete records from the old nameserver immediately

Adding Email Records

When setting up email (MX, SPF, DKIM, DMARC records), partial propagation can cause temporary delivery issues. Test thoroughly after allowing time for propagation before relying on the new configuration.

Troubleshooting Propagation Issues

If your DNS changes don't seem to be propagating:

Verify the change was saved: Check your DNS provider's control panel to confirm the record is correct
Check the authoritative nameserver directly: Use dig @ns1.yourprovider.com yourdomain.com to query directly
Wait for the full TTL: Check the previous TTL value and wait that long
Clear your local cache: Your own computer might be caching the old value
Try a different network: Your ISP might be caching aggressively
Use our propagation tool: Check if the issue is global or local to your location