Paste the records as you wrote them — BIND zone file, Terraform cloudflare_record, Kubernetes YAML, a .env line. 19 checks run on every v=spf1, v=DMARC1 and v=DKIM1 string, including the May 2026 DMARCbis changes (RFC 9989 / RFC 9990 obsoleted RFC 7489: pct= removed, np= and t= added). No DNS query, no upload, no account — the domain does not have to resolve yet.
Same engine as the VS Code extension, byte for byte — the file below is ext/engine.js and ext/rules.json from the published extension. Everything runs in your browser; nothing is sent anywhere. Sources for every finding: RFC 7208, RFC 1035, RFC 6376, RFC 8301, and RFC 9989 / RFC 9990 (IETF, May 2026). Extension: getreadystack.com/tools/spf-dmarc-record-lint