DNS Change Tracker

Track a DNS change across 14 public resolvers and see which networks still return the old value, which have switched, and which show something unexpected.

Track a DNS change across resolvers

A DNS change tracker compares the value you moved away from with the value you expect now. Instead of only showing raw DNS answers, it labels each resolver as seeing the old value, the new value, both, something else, no record, or a failure.

Use it during site moves, mail migrations, CDN cutovers, and provider changes when the question is not just "what is DNS returning?" but "who still has the previous answer cached?". If you do not want to keep refreshing the page, create a one-shot email alert and WhereIsDNS will tell you when the move finishes.

When this is useful

• Website migrations: compare the old A record IP with the new server IP.
• Mail migrations: compare old MX hosts with Google Workspace, Microsoft 365, Fastmail, or another new provider.
• CDN launches: compare the previous CNAME target with the new edge hostname.
• TXT verification: confirm SPF, ownership, or service-verification records have switched.

How to read the result

New means the resolver returned the value you expect now. Old means it still returned the previous value. Mixed means both old and new appeared in the same answer set. Other means the resolver answered, but not with either value. Missing means no record or NXDOMAIN. Failed means timeout, error, or SERVFAIL.

FAQ

Do I need to know the old value?

Yes. The tracker is strongest when you know what changed from and what changed to. If you only know the new value, run the regular propagation checker first and inspect the unexpected answers.

Can it track MX records?

Yes. For MX records you can enter the mail host, such as aspmx.l.google.com, and the tracker ignores the priority number while matching.

Why does one resolver show both old and new?

Some record types can legitimately return multiple values. During a migration, a mixed answer often means old records were added to rather than replaced, or that round-robin answers still include the previous target.

Does this save history?

This first version is a live comparison only. It does not require an account and does not store your tracker unless you create a separate shareable report from the normal lookup flow.

What should I do if most resolvers still show old?

Confirm the authoritative DNS provider and nameservers first. If all public resolvers still show the old value, the change may not be published in the zone the internet actually uses.