Why run a DNS propagation test?
When you modify a DNS record, the change isn't instantly visible everywhere. Each DNS resolver caches responses for a duration defined by the TTL (Time To Live). Testing propagation lets you:
- Confirm a change is live before switching a service over
- Identify lagging resolvers that still hold the old value
- Document the progression to reassure clients or stakeholders
- Anticipate issues before they impact your users
Technical reminder DNS propagation is not an active broadcast. Resolvers don't sync with each other. Each cache expires independently according to its TTL, then queries the authoritative server for the new value.
How to use the propagation test in 3 steps
Step 1: Enter domain and record type
Type your domain name in the search field. Then select the DNS record type you want to check:
- A: Server IPv4 address
- AAAA: IPv6 address
- MX: Mail servers
- TXT: Text records (SPF, DKIM, verifications)
- CNAME: Alias to another domain
- NS: Authoritative name servers
Step 2: Run multi-resolver check
Click "Test" to simultaneously query:
| Resolver | IP | Region |
|---|---|---|
| Google Public DNS | 8.8.8.8 | Global |
| Cloudflare | 1.1.1.1 | Global |
| Quad9 | 9.9.9.9 | Global |
| OpenDNS | 208.67.222.222 | Global |
| Yandex DNS | 77.88.8.8 | Russia/Europe |
| Authoritative server | Varies | Source |
Step 3: Analyze results
For each resolver, you get:
- Current value: The response returned by this resolver
- Remaining TTL: Time until cache expiration
- Status: Match or mismatch with authoritative value
- Timestamp: When the data was fetched
Understanding TTL and propagation
What is TTL?
TTL (Time To Live) tells resolvers how long they can cache a response. A TTL of 3600 means "keep this answer for 1 hour before asking me again".
| TTL (seconds) | Duration | Recommended use |
|---|---|---|
| 60-300 | 1-5 min | Frequent changes, migrations |
| 3600 | 1 hour | Standard usage |
| 86400 | 24 hours | Stable records |
Preparing for a DNS change
To minimize propagation time:
- 24-48h before: Lower TTL to 300 seconds
- Wait for old caches to expire (based on previous TTL)
- Make the change on the authoritative server
- Check propagation with this tool
- After confirmation: Raise TTL back to normal
Propagation test use cases
Host migration
Scenario: You're moving your website from host A to host B.
- Lower A/AAAA record TTL 24 hours before
- Configure the new server at host B
- Update A record to point to new IP
- Test propagation to track the switchover
- Verify all resolvers point to B
Email authentication setup
Scenario: You're adding SPF, DKIM and DMARC for your domain.
- Publish TXT records on your DNS
- Test propagation for each record
- Confirm major resolvers see the correct values
- Run an email test to validate
Production incident
Scenario: Your site is down and you've changed the IP urgently.
- Run propagation test immediately
- Identify resolvers still pointing to old IP
- Communicate remaining TTL to your team
- Document progression for post-mortem
Interpreting results
All resolvers show the new value
Propagation is complete. You can:
- Close the incident or migration ticket
- Inform stakeholders
- Raise TTL back if you lowered it
Some resolvers still show old value
This is normal during propagation. Check:
- Remaining TTL on those resolvers
- That authoritative value is correct
- Be patient until caches expire
NXDOMAIN on some resolvers
The record is not found. Possible causes:
- Record doesn't exist on authoritative server
- Negative cache (resolver memorized "doesn't exist")
- DNS configuration error
SERVFAIL or timeout
The resolver can't get a response. Check:
- Your NS server configuration
- Authoritative server accessibility
- Potential network issues
FAQ - Frequently asked questions
Q: What is DNS propagation?
A: DNS propagation is the time it takes for DNS record changes to become visible across all DNS servers worldwide. It's not an active broadcast - caches simply expire according to their TTL, then fetch the new value.
Q: How long does DNS propagation take?
A: Duration depends on the configured TTL. With a 300-second TTL (5 minutes), propagation is nearly instant. With an 86400-second TTL (24 hours), some resolvers may keep the old value for up to 24 hours.
Q: How can I speed up DNS propagation?
A: You cannot force propagation, but you can prepare for it:
- Lower TTL to 300s a few hours before the change
- Make the modification
- Wait for caches to expire
- Raise TTL back to reduce load on your servers
Q: Why do some resolvers show the old value?
A: Each resolver caches responses for the duration of the TTL. If TTL was 3600 seconds, a resolver that cached the response 10 minutes ago will keep it for another 50 minutes.
Q: What DNS record types can I test?
A: All types: A (IPv4), AAAA (IPv6), MX (email), TXT (SPF, DKIM), CNAME (alias), NS (name servers), SOA (authority), CAA (certificates), SRV (services), PTR (reverse DNS).
Q: Is the propagation test free?
A: Yes, 100% free with no signup required. Test as many domains as you want. Results are instant and shareable.
Q: What should I do if NXDOMAIN appears?
A: NXDOMAIN means the resolver cannot find the record. Check that the record exists on your authoritative server and wait for the negative cache to expire.
Complementary tools
| Tool | Purpose |
|---|---|
| DNS Lookup | Query a specific record type |
| Domain Check | Complete DNS configuration audit |
| Email Tester | Verify SPF, DKIM, DMARC from a real email |
| SPF Inspector | Analyze and validate your SPF record |
| Reverse IP | Find PTR record for an IP address |
Useful resources
- RFC 1035 - Domain Names Implementation - Core DNS specification
- RFC 2181 - Clarifications to DNS - DNS behavior clarifications
- Google - Flush DNS Cache - Purge Google DNS cache
- Cloudflare - Purge Cache - Purge Cloudflare cache