Every CheckItNowTools tool documents how its result is computed. This page summarises the methodological foundations shared across the platform. For per-tool computation details, see the dedicated Methodology page.
Inspection techniques
- Live HTTP / HTTPS requests issued at the moment of the check.
- DNS-over-HTTPS (DoH) queries against authoritative public resolvers.
- TLS handshakes performed directly against the target host.
- Browser feature detection via standard web platform APIs.
- Public registry queries (RDAP, port-43 WHOIS) routed through IANA bootstrap data.
Validation methods
- Cross-resolver comparison for DNS records to detect propagation mismatches.
- Cross-feed comparison for reputation and blacklist signals.
- Certificate chain inspection against the host's SAN coverage.
- Header response scoring against the OWASP Secure Headers project.
Public records used
- Domain registration data from RDAP (IANA-bootstrapped) with port-43 WHOIS fallback.
- Routing data from public RIR allocations and ASN ownership records.
- Certificate transparency-aware lookups where applicable.
- Public DNSBL feeds for reputation signal aggregation.
Browser APIs
- navigator, screen, document, Intl, performance, and WebRTC where exposed.
- Browser-reported user-agent strings are heuristic — never authoritative.
- Privacy modes, extensions, and browser-level lockdowns can change what is detectable.
Assumptions
- Targets are reachable from the platform's egress network at the moment of the check.
- Upstream registries and feeds are returning fresh, non-stale data.
- The user has supplied a syntactically valid input (domain, IP, URL).
Limitations
- Caching, TTLs, and DNS propagation can mask recent changes.
- IP geolocation is city-accurate at best and may misidentify mobile / VPN networks.
- Reputation feeds carry a non-zero false-positive rate.
- Certificate inspections do not include OCSP / CRL chase or full chain installation tests.
- Page screenshots and visual-similarity detection are not part of the methodology.
Last reviewed: June 2026.