DNS Propagation: Why Changes Take Time

When you update your DNS records — whether changing nameservers, adding a new subdomain, or updating an IP address — the changes don't take effect instantly. This delay is called DNS propagation, and understanding it helps set realistic expectations when making DNS changes.

What is DNS Propagation?

DNS propagation is the time it takes for DNS changes to be updated across all DNS servers worldwide. When you make a change to your DNS records, it doesn't instantly appear everywhere because:

1. DNS is distributed — There's no single DNS database. Millions of DNS servers around the world cache records.
2. Caching is essential — Without caching, every DNS query would have to go to authoritative servers, creating massive load.
3. TTL controls cache duration — Each DNS record has a TTL (Time To Live) that tells servers how long to cache it.

How Long Does Propagation Take?

DNS propagation typically takes anywhere from a few minutes to 48 hours, depending on several factors:

Change Type	Typical Time	Maximum Time
A/AAAA Record Update	Minutes to hours	24-48 hours
New Subdomain	Minutes to hours	24 hours
MX Record Change	Minutes to hours	24-48 hours
Nameserver Change	12-24 hours	48-72 hours
New Domain Registration	1-4 hours	24 hours

Understanding TTL

TTL (Time To Live) is the most important factor in propagation speed. It's a value in seconds that tells DNS resolvers how long to cache a record before checking for updates.

Common TTL Values

300     = 5 minutes   (good for records that change often)
3600    = 1 hour      (common default)
14400   = 4 hours     (typical for stable records)
86400   = 24 hours    (maximum recommended)
604800  = 1 week      (rarely used, not recommended)

How TTL Affects Propagation

If your A record has a TTL of 3600 (1 hour), DNS servers will cache it for up to 1 hour. When you change the record:

• Servers that just cached the old record may take up to 1 hour to get the new one
• Servers whose cache expired will get the new record immediately
• Servers that never cached it will get the new record immediately

How to Speed Up Propagation

1. Lower TTL Before Changes

Plan ahead: reduce TTL 24-48 hours before making changes, then restore it afterward.

2. Clear Your Local DNS Cache

Windows:

ipconfig /flushdns

macOS:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Linux:

sudo systemd-resolve --flush-caches

3. Clear Browser DNS Cache

Browsers maintain their own DNS cache. In Chrome, visit chrome://net-internals/#dns and click "Clear host cache".

4. Use a Different DNS Resolver

Temporarily switch to a public DNS like 1.1.1.1 or 8.8.8.8 that may have already updated.

Checking Propagation Status

You can check if your DNS changes have propagated using command-line tools:

Using dig

# Check against a specific DNS server
dig @8.8.8.8 example.com A

# Check against multiple servers
dig @1.1.1.1 example.com A
dig @9.9.9.9 example.com A
dig @208.67.222.222 example.com A

Using nslookup

nslookup example.com 8.8.8.8
nslookup example.com 1.1.1.1