How DNS Propagation Works

What is DNS Propagation?

When you change DNS records, the update does not take effect instantly worldwide. DNS propagation is the time it takes for DNS changes to spread across all DNS servers globally.

Why It Takes Time

• TTL (Time to Live) — DNS records have a TTL value (in seconds) that tells resolvers how long to cache the record. A TTL of 3600 means resolvers keep the old record for up to 1 hour.
• Multiple cache layers — ISP resolvers, corporate DNS servers, browser caches, and OS caches all store DNS records independently.

Typical Propagation Times

• TTL 300 (5 minutes) — most changes visible within 5-30 minutes
• TTL 3600 (1 hour) — fully propagated within 1-4 hours
• TTL 86400 (24 hours) — can take up to 48 hours for full propagation
• Nameserver changes — always 24-48 hours regardless of TTL

Speeding Up Propagation

1. Lower the TTL to 300 seconds 24-48 hours before making changes
2. Make your DNS change
3. Wait for propagation
4. Raise TTL back to normal (3600-86400)

Checking Propagation

# Check from different DNS servers
dig @8.8.8.8 example.com      # Google
dig @1.1.1.1 example.com      # Cloudflare
dig @9.9.9.9 example.com      # Quad9

# Check from your server
dig example.com +short

Flush Local DNS Cache

# macOS
sudo dscacheutil -flushcache

# Windows
ipconfig /flushdns

# Linux (systemd-resolved)
sudo resolvectl flush-caches