DNS Propagation Checker

Query DNS-over-HTTPS resolvers (Cloudflare 1.1.1.1, Google 8.8.8.8, Quad9) in parallel for a domain and record type. Reports whether answers agree, each resolver's values, and response time.

Features

• GET /check - parallel DoH queries across three public resolvers
• Supports A, AAAA, CNAME, MX, TXT, NS record types
• Agreement summary plus per-resolver values and latency

API Reference

GET /check

domain string (required) - Hostname to query (no scheme).

type string (required) - Record type: A, AAAA, CNAME, MX, TXT, or NS.

Example Request

curl "https://your-worker.workers.dev/check?domain=example.com&type=A"

Success Response

{
  "domain": "example.com",
  "type": "A",
  "agreement": true,
  "resolvers": [
    { "name": "Cloudflare", "values": ["93.184.216.34"], "responseTimeMs": 42, "error": null }
  ]
}

Error Codes

• 400 - INVALID_DOMAIN, INVALID_TYPE
• 502 - DNS_ERROR

Use Cases

• Verify DNS changes have propagated globally after a cutover
• Compare resolver behavior during TTL or nameserver migrations
• Debug split-horizon or stale cache issues across providers

Limitations

• Queries three public DoH endpoints only; not exhaustive global propagation
• Single record type per request
• Resolver errors return partial results rather than failing the whole request

Deployment

Local Development

cd apps/experiments/dns-propagation-checker
npm install
npm run dev

Configuration

No bindings required beyond the Workers runtime.

Cloudflare Features Used

• Workers
• DNS over HTTPS