Email & DNS

DNS TTL Change Planner

Plan when to lower and later restore a DNS cache lifetime around a change.

Calculations run in your browser. The tool does not send your inputs to a server.

01Your inputs

Local workspace

Start with the sample below, or enter your own values.

Current TTL (seconds)Enter a numeric value using the unit shown in the label.

Temporary TTL (seconds)Enter a numeric value using the unit shown in the label.

TTL after the change (seconds)Enter a numeric value using the unit shown in the label.

02Your result

Your result will appear here. Choose an action after checking your inputs.

A quick guide

How to use this tool

Check the example and the unit beside each input.
Enter your values and choose Plan.
Review the result and assumptions, then copy what you need.

Reset example restores the starting values. Clear removes text and number inputs, returns choices to their first valid option, and removes the result.

Reference guide

Explanation and worked examples

Lower the TTL at least one current-TTL period before changing the record. After the change, wait at least the temporary TTL before assuming compliant caches have refreshed.

Use in day-to-day IT work

Schedule a DNS migration so existing cached answers can expire.

Checks before applying the result

Lower TTL at least one old-TTL period before changing the answer, and confirm that lower TTL is live at every authoritative server.
Negative answers and application caches have separate lifetimes. Keep the old endpoint available through the overlap period.

New to the terminology?

SPF: Sender Policy Framework: authorises sending hosts for a domain used by SMTP.
MTA-STS: A published policy for authenticated TLS delivery to declared MX hosts.
TTL: How long a DNS answer may normally remain cached.

Keep exploring

How calculations work and where the models stop →