How to use it
- Type the exact name you changed in Domain name, such as
www.example.com. - Pick the Record type: A, AAAA, CNAME, MX, TXT, NS or CAA.
- Type the new value in Expected value (optional), for example
203.0.113.10, and press Check. - Read the verdict and Longest TTL seen, then press Check again later.
What propagation really is
A DNS change doesn't travel outward across the world. Your DNS host's name servers serve the new value the moment you save it. What lags behind are resolvers that looked the name up earlier: each may keep its cached answer until that answer's TTL runs out (RFC 1035). So the wait is set by the TTL the old record had, not by distance.
What this checker asks
Seven public resolvers, each queried over encrypted DNS-over-HTTPS from this site's server on Cloudflare: Cloudflare, Google Public DNS, Quad9, AdGuard DNS (unfiltered), OpenDNS (Cisco), Mullvad DNS and AliDNS. These services are anycast, so the query reaches the location nearest the Cloudflare data centre that ran the check. Other locations of the same resolver keep their own caches.
Six regional rows, labelled Google, as seen from the United States, Europe (Germany), Asia (Japan), India, South America (Brazil) and Australia. Each asks Google Public DNS with an EDNS Client Subnet hint (RFC 7871): a /24 network from that region, so name servers that answer by location reply as if the visitor were there. No server in that country is actually asked.
That makes 13 views in total, not hundreds.
Reading the table
| Label | Meaning |
|---|---|
| Matches / Doesn't match | With an expected value: whether this view returns it |
| Majority | Without one: this view gives the most common answer |
| Differs | Without one: this view disagrees with the most common answer |
| Error | The resolver timed out (4-second limit) or failed |
| TTL left (column) | How long this view may keep its current answer |
Matching ignores case but is otherwise exact. For MX you can type only the host name, mail.example.com, and it matches 10 mail.example.com. For TXT, type the whole string. If a name has several A records, one matching address is enough.
Worked example
You move www.example.com from 198.51.100.20 to 203.0.113.10. The old A record had a TTL of 3600 seconds. Ten minutes later you check with 203.0.113.10 as the expected value.
Nine views already return the new address; four still return the old one. The verdict reads 9 of 13 return your expected value. The four old rows show about 50 minutes under TTL left: by then each must ask your name servers again and will get the new address. Longest TTL seen covers every answer, new ones included, so it can be longer than the old answers really need.
Making the next change faster
- A day before the change, lower the record's TTL, for example to 300 seconds, and wait out the old TTL so caches hold the short one.
- If every view matches but your computer still gets the old value, flush your device's DNS cache or restart the router.
- Name server (NS) changes at the registrar depend on the TTL of the NS records in the parent zone, which you don't control. Check the delegation with a WHOIS lookup.
Questions
- Why do the regional rows show different IPs for big sites?
- Sites behind content delivery networks hand out an address close to the visitor. That's expected, and the verdict calls it different answers rather than an error.
- Why does one resolver still show the old value?
- Its cache at the location that answered still holds it until TTL left reaches zero. Another location of the same resolver may already have the new value.
- Does it check my ISP's resolver?
- No. The checker only reaches public resolvers over DNS-over-HTTPS. Your ISP's resolver answers your own device, for example through
nslookupon your computer. - What does 'No records' mean?
- The resolver answered, but there's no record of that type at that exact name.
example.comandwww.example.comare separate names with separate records. - Does the regional hint reveal my location?
- No. The subnets sent are fixed networks of large carriers and universities in each region. Your own address isn't part of the query. For one resolver at a time with more record types, use the DNS lookup.