Question 1

What does DNS propagation actually mean?

Accepted Answer

When you change a DNS record, the change has to propagate from your authoritative nameserver out to every resolver cache worldwide. Each resolver caches the OLD record until its TTL (Time-To-Live) expires, then it fetches the new one. With a 300-second TTL, propagation takes ~5 minutes for most resolvers. With a 24-hour TTL, it takes a full day. The tool compares answers from two major resolvers (Cloudflare + Google) — if they match, propagation is complete for those resolvers. If they don't match, one still has the old cached value.

Question 2

Why only two resolvers?

Accepted Answer

Browser-based tools can only fetch from CORS-allowed DoH endpoints, and Cloudflare + Google are the two majors that enable CORS for the JSON API. Server-based tools (like dnschecker.org) query 30+ resolvers globally; this tool gives you the most-used 60% of resolvers. Two-resolver match is a strong propagation signal — if both major resolvers agree, smaller resolvers are usually within minutes.

Question 3

What TTL should I set for fast updates?

Accepted Answer

For routine records: 3,600 seconds (1 hour) is the standard. For records you'll change soon (planning a migration, swapping IPs, A/B testing): drop TTL to 300 seconds (5 min) 24-48 hours before the change so resolvers have already cached the short TTL when you flip the record. After the change is stable, raise TTL back to 3,600 to reduce resolver load. Going below 300 has diminishing returns; some resolvers ignore TTLs under 60 seconds.

Question 4

How long does propagation actually take?

Accepted Answer

Within the TTL window for cached resolvers (5 min for TTL=300, 1 hour for TTL=3,600). For resolvers that haven't yet cached the record (cold cache), propagation is instant — the resolver fetches authoritative on the first miss. The 'up to 48 hours' figure you see online is the worst case: a recursive resolver with stale TTLs from before you set the record. In modern global DNS, 95% of resolvers reflect changes within their TTL window.

Question 5

Why does Google show different from Cloudflare?

Accepted Answer

Three reasons. (1) Stale cache: one resolver has cached the old record and TTL hasn't expired. (2) Anycast routing: 'Cloudflare 1.1.1.1' is actually 200+ datacenters worldwide; the response you get depends on which is geographically closest. Same for Google. So the tool's two answers may come from different physical locations with different cache states. (3) Edge propagation lag: large DNS providers replicate authoritative records to their global edge in waves, taking 30-60 seconds.

Question 6

Does this tool log my queries?

Accepted Answer

Digital Heroes doesn't log. Cloudflare and Google DoH endpoints log queries per their respective resolver privacy policies.

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