Free domain checkers

Instant SPF, DKIM, DMARC, MX, DNS A, CAA vs live cert issuer, MTA-STS / MTA STS checker (decoded policy), TLS-RPT / TLS reporting, BIMI, SSL, security header, open port, and performance checks — no login. On fail/warn you get copy-paste DNS examples for that domain. Add it free and the same fix hints stay on domain details.

Full check / domain monitoring Domain monitoring pulse — SPF + DKIM + DMARC + MX + SSL + CAA vs live issuer (email auth flock) SPF checker Free SPF checker — include tree + 10 DNS-lookup limit, missing/+all warn DKIM / monitoring DKIM monitoring — common selectors, missing/empty public key warn DMARC / monitoring DMARC monitoring — _dmarc policy present, p=none warn, spoofing posture MX / monitoring MX monitoring — inbound exchangers present, priorities + hosts DNS A / monitoring DNS monitoring: does the hostname still have an IPv4 A record Apex / monitoring Apex monitoring — A/AAAA at the bare domain + CNAME-at-apex warning CAA record / tester CAA record checker / CAA tester — allow-list present + does it permit the live TLS issuer MTA-STS / MTA STS checker MTA-STS checker / MTA STS checker — DNS id + HTTPS policy (mode, mx, max_age) still live TLS-RPT / TLS reporting TLS-RPT checker / TLS reporting — _smtp._tls v=TLSRPTv1 rua still published BIMI / monitoring BIMI monitoring — default._bimi inbox brand-mark DNS still published SSL / expired / monitoring SSL days left or expired + live issuer (pair with CAA) Website / uptime / HTTP status HTTP status / uptime pulse — HTTPS status + title Expiry / WHOIS monitoring Domain expiry monitoring — registration runway via public RDAP/WHOIS path Security headers / monitoring Security headers monitoring — nosniff, HSTS, X-Frame-Options, HTTPS redirect still live Open port scanner Risky TCP ports — FTP, Telnet, MySQL, Postgres, Redis, MongoDB TTFB / performance monitoring Website performance monitoring — TTFB-style HTTPS first-byte pulse still sane

Guides

Plain English on what each record means.

Pair a free check with a short guide: domain monitoring, email authentication monitoring, email authentication, SPF monitoring, SPF, DKIM monitoring, DKIM, DMARC monitoring, DMARC, MX monitoring, MX, DNS monitoring, DNS A, apex monitoring, apex / zone apex, CNAME at apex, CAA record, CAA monitoring, MTA-STS / MTA STS checker, MTA-STS monitoring, BIMI monitoring, BIMI, SSL certificate monitoring, SSL certificate expired, domain expiry / WHOIS monitoring, domain expiry (RDAP), security headers monitoring, HSTS, X-Frame-Options, X-Content-Type-Options, HTTPS redirect, open ports / open port scanner, security headers & open ports, TLS-RPT / TLS reporting, TLS-RPT monitoring, HTTP status monitoring, uptime monitoring, website monitoring, website performance monitoring, TTFB, performance.

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