Theoretical cache window · not a propagation test
DNS TTL waiting window estimator
Estimate a theoretical DNS record cache window from a TTL and optional local-cache assumption. No DNS lookup or global propagation measurement is performed.
Estimate a planning window from a DNS record's TTL and an optional extra local-cache allowance. This worksheet does not query DNS or test resolvers.
Enter cache assumptions
Enter both values in seconds. Use 0 if you have no additional local-cache allowance to model.
How to read the estimate
DNS TTL is the period for which a DNS record may be cached. After a record changes, a recursive resolver that fetched the old answer just before the change could retain it for up to the old record TTL. The first result shows that TTL window. The optional second result adds your local-cache allowance after the resolver window as a deliberately simple, serial planning scenario; actual cache layers can overlap, expire differently, or retain stale data.
If planning a record change, check the record's current TTL and your DNS provider's instructions. Lowering TTL shortly before a change does not erase answers already cached under the earlier TTL; allow the previous TTL to expire before relying on the lower value. This estimate does not cover nameserver/delegation changes, registrar processes, DNSSEC issues, provider-specific minimums, or every resolver's behavior.
Limits
This page does not inspect authoritative records, contact recursive resolvers, or measure global visibility. A result is a theoretical waiting window from entered assumptions, not a guarantee that every visitor will see an update by that time. Local operating-system, browser, router, and application caches may add delay. Verify the changed record through the authoritative provider and suitable DNS lookup tools from the networks that matter to you.
For Cloudflare's documented TTL behavior and the distinction between proxied records, DNS-only records, and nameserver TTL, see its Time to Live documentation (updated April 16, 2026; checked November 3, 2026). Cloudflare notes that local DNS caching can make a change take longer than the configured TTL, and that nameserver TTL is separate.
For other website planning tools, see the hosting needs estimator and domain renewal worksheet.
How it works
Enter a DNS record TTL in seconds and an additional local-cache allowance in seconds, or use zero if you do not want to model an extra allowance. The output shows the record TTL window and a separate serial-cache scenario. It does not query DNS or predict when every resolver will update.
Good to know
Does this estimate show when DNS has propagated worldwide?
No. It only converts your entered TTL and optional local-cache allowance into theoretical durations. It does not contact authoritative or recursive DNS servers, measure resolver behavior, or guarantee when users will see a change.
Why can a DNS change take longer than the record TTL?
A resolver may have cached the old answer shortly before a change, and local operating-system, router, browser, or application caches may add delay. Providers and resolvers can also apply behavior this simple worksheet does not model.
Is nameserver TTL the same as a DNS record TTL?
Not always. Cloudflare documents nameserver TTL as a separate feature that affects its nameservers and custom nameservers. Check your provider's documentation and the exact record or delegation being changed.
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