Key facts
- DNS changes do not travel anywhere: caches expire, and resolvers then fetch the new answer.
- The TTL (time to live) on a record tells resolvers how long they may cache it, in seconds.
- A TTL of 3600 means caches can keep the old answer for up to an hour after you change it.
- Changing nameservers can take longer than changing a record because the parent zone (such as .uk) also has a cache time.
- Lowering TTLs to 300 seconds a day before a planned move makes the switch almost instant.
- Your own computer and router cache DNS too, so flush them when testing.
What DNS propagation really is
DNS is the system that turns a name like yourbusiness.co.uk into the IP address of a web server, and tells the world which servers handle your email. When you change a DNS record, for example to point your website at a new host, the change happens instantly on your authoritative nameservers. Nothing has to "spread".
The delay people call propagation is caching. Internet providers, mobile networks, Google's 8.8.8.8, Cloudflare's 1.1.1.1 and your own router all keep a copy of the answer they last looked up, so they do not have to ask again every time. Each copy expires when its timer runs out. Until then, some visitors see the old site and some see the new one. That is why your phone on 4G might show the new site while your office PC still shows the old one.
TTL: the setting that decides how long it takes
Every DNS record has a TTL (time to live) in seconds. Common values are:
| TTL | Meaning |
|---|---|
| 300 | Caches refresh every 5 minutes |
| 3600 | Up to 1 hour of old answers |
| 14400 | Up to 4 hours |
| 86400 | Up to 24 hours |
The catch is that a resolver obeys the TTL it saw when it cached the record. If your A record had a TTL of 86400 yesterday and you lower it to 300 today, anyone who cached it yesterday can keep the old answer for up to a day. So lower the TTL at least one full old-TTL period before the change.
Nameserver changes are slower still. When you move DNS to a new provider, the registry for your domain ending (Nominet for .uk, Verisign for .com) publishes the new NS records, and resolvers cache those for the registry's own TTL, which you cannot change. Allow up to 48 hours for a nameserver switch.
How to plan a DNS change with no downtime
- Export your current zone. Before touching anything, copy every record: A, AAAA, CNAME, MX, TXT (including SPF, DKIM and DMARC), SRV and any verification records for Microsoft 365 or Google. Missing an MX or TXT record is the most common way a website move breaks email.
- Lower TTLs. Set the records you will change to 300 seconds and wait out the old TTL.
- Keep the old server running. Leave the old hosting live for at least 48 hours after the switch so stragglers still get a working site and email.
- Make the change. Update the record or the nameservers.
- Check from outside. Use a global checker such as whatsmydns.net, or run nslookup yourdomain.co.uk 8.8.8.8 and nslookup yourdomain.co.uk 1.1.1.1 to see what public resolvers return.
- Raise TTLs again to an hour or more once everything is stable.
Seeing old results on your own computer
If a checker shows the new IP but your browser still shows the old site, the cache is local. Try these in order:
- Windows: open Command Prompt and run ipconfig /flushdns.
- Mac: run sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder in Terminal.
- Chrome keeps its own cache: visit chrome://net-internals/#dns and click Clear host cache.
- Restart the office router, which often caches DNS for every device behind it.
- Test on a phone with Wi-Fi turned off to bypass the office network completely.
If you still see the old site after 48 hours, it is not propagation. Something is set wrong: a record on the old DNS provider, a CDN or proxy such as Cloudflare in front of the site, or a hosts file entry on the PC.
When to call dijitul support
DNS mistakes are easy to make and slow to undo, because the wrong answer gets cached as well. Call us before a website move, an email migration to Microsoft 365, or a change of registrar, and we will audit the zone, lower TTLs, make the change and confirm it from several public resolvers. If email has stopped or the site is still wrong after two days, we can trace the cause remotely.
One-off DNS work is £45 an hour + VAT. Ongoing domain and DNS management is part of our domain and DNS support, and moving a site is covered under website migration support. See our plans or get in touch.
Frequently asked questions
How long does DNS propagation take?
For a record change, as long as the record's previous TTL, often between 5 minutes and 24 hours. For a nameserver change, allow up to 48 hours because the domain registry's own cache time applies. dijitul lowers TTLs in advance so planned changes take minutes.
Can I force DNS to propagate faster?
You cannot clear other people's caches. You can only lower the TTL before the change, then flush your own computer and router cache. Some public resolvers, including Google and Cloudflare, offer a page to request a cache purge for a domain.
Why does my website work on my phone but not my PC?
Your phone on mobile data uses a different resolver that has already picked up the new record, while your PC or office router still holds the old answer. Run ipconfig /flushdns on Windows and restart the router.
Will changing DNS take my email down?
Only if the MX, SPF, DKIM or autodiscover records are lost or changed by mistake. Copy the whole zone before changing nameservers. dijitul checks every mail record during a DNS move so email keeps flowing.
Does dijitul manage DNS for small businesses?
Yes. dijitul support plans and audits DNS changes, sets up SPF, DKIM and DMARC, and handles nameserver and registrar moves for UK businesses. One-off work is £45 an hour + VAT, and larger migrations are quoted.
Related
Get it fixed
One-off fixes are £45 an hour + VAT. You'll know the likely cost before we start.