You just pointed your domain to a new host, updated a DNS record, or launched your site - and now you are waiting. Your neighbour can see the new site, but you are still seeing the old one. What is going on?
The answer is DNS propagation, and it is one of the most commonly misunderstood parts of owning a domain. Here is a clear explanation of what it is and why it happens.
What Is DNS?
DNS stands for Domain Name System. It is essentially the phone book of the internet. When someone types your domain name into a browser, their computer does not actually know where your website lives - it has to look up the IP address (the numeric address of your server) by querying the DNS system.
DNS records are stored on name servers - specialized servers that hold authoritative information about where your domain points. When you register a domain and set up hosting, you configure these records to direct traffic to the right place.
How Propagation Works
Here is the key thing to understand: DNS information is not stored in just one place. Internet service providers (ISPs) and networks around the world maintain their own local caches of DNS records. These caches are copies of the authoritative records, stored temporarily to speed up lookups and reduce load on the global DNS system.
When you make a change to your DNS records - such as updating an A record to point to a new server - that change is immediate on your authoritative name server. But every ISP and recursive DNS resolver around the world still has the old information cached. They will not update until their cache expires and they go back to fetch the current record.
This process of the updated record spreading across all these cached systems worldwide is called propagation.
What Is TTL and Why Does It Matter?
TTL stands for Time to Live. It is a value (measured in seconds) attached to every DNS record that tells caching resolvers how long to store the record before fetching a fresh copy.
A TTL of 86400 means 86,400 seconds - or 24 hours. If your A record has this TTL and you change it, some resolvers may hold onto the old value for up to 24 hours before they check for an update.
Pro tip: If you know you are planning a DNS change - like migrating to a new host - lower your TTL to 300 (5 minutes) a day or two before you make the switch. This means resolvers will refresh the record much faster after your change, dramatically cutting propagation time. After the change is stable, you can raise the TTL again.
Why Does Propagation Take So Long?
Full propagation typically takes anywhere from a few minutes to 48 hours, depending on:
- Your TTL value - lower TTLs propagate faster
- Your ISP's caching behaviour - some ISPs ignore TTL and cache records longer than they should
- Geographic distance - DNS changes spread outward from authoritative servers, so far-flung locations may update last
How to Check Propagation Status
You do not have to sit and refresh your browser hoping for the best. Several free tools let you check how your DNS records look from different locations around the world:
- whatsmydns.net - shows your record from dozens of global locations simultaneously
- dnschecker.org - similar tool with a clean interface
- Google Public DNS (8.8.8.8) - you can flush and test via Google's own DNS flush tool at developers.google.com/speed/public-dns/cache
Tips for Minimizing Disruption During a DNS Change
- Lower your TTL at least 24 hours before making the change
- Make DNS changes during off-peak hours (evenings or weekends for Canadian sites)
- Keep your old hosting active and functional until propagation is complete - do not cancel it the moment you update the records
- Test your site using a hosts file edit or the new host's temporary URL before switching DNS
At dotCanada, we walk customers through DNS changes during domain transfers and hosting migrations. Getting it right the first time saves hours of confusion. If you ever need help with a tricky DNS situation, our support team is here to assist.
