HTTP headers
Follow the redirect chain, see response headers and timing, and grade the security headers.
Frequently asked questions
What is the difference between 301, 302, 307 and 308?
301 and 308 are permanent redirects; search engines move ranking to the new URL. 302 and 307 are temporary. 307 and 308 also keep the request method, so a POST stays a POST.
Which security headers matter most?
Strict-Transport-Security forces HTTPS, Content-Security-Policy limits where scripts can load from, and X-Content-Type-Options stops MIME sniffing. Referrer-Policy and Permissions-Policy add privacy controls.
Why is the first byte slow?
Time to first byte is server processing time plus one round trip. If DNS, connect and TLS are fast but TTFB is high, the application or database is the bottleneck.
Tools
DNS propagation checkerQuery resolvers around the world and the zone's authoritative nameservers in one go, and see on the map where your change has arrived.PingRound-trip time and packet loss from our server. Use TCP mode when a host drops ICMP.TracerouteThe path packets take from our server to the target, hop by hop, with the network (ASN) each router belongs to.SSL / TLS checkCertificate validity, chain, hostname match and which TLS versions the server accepts.Port checkIs a TCP port reachable from the internet? Test a server, or your own connection to confirm port forwarding.WHOIS lookupRegistration details for a domain or the owner of an IP range, straight from the registry's WHOIS servers.Mail & blacklistMX, SPF, DMARC and DKIM for a domain, plus a check of its mail servers against public DNS blocklists.Subnet calculatorEnter an address with a prefix or a mask, for example 192.168.10.37/26 or 10.0.0.1 255.255.240.0.What is my IP?This is the address websites see when you connect to them.