15 free tools, all running entirely in your browser.
Free CIDR calculator — convert CIDR notation into its network address, broadcast address, and usable IP range.
Convert between a CIDR prefix and a dotted-decimal subnet mask, either direction.
Convert an IPv4 address between dotted-decimal and binary notation, either direction.
Free tool to show your current public IP address, whether it’s IPv4 or IPv6, and its approximate location.
Clean up and reformat a MAC address into colon, hyphen, or dot notation.
Free IP address lookup — enter any IP and see its approximate location, instantly.
Free DNS lookup — check A, AAAA, MX, TXT, NS, CNAME, or SOA records for any domain, instantly.
Find the hostname associated with an IP address — a PTR record (reverse DNS) lookup.
Look up and explain a domain’s SPF record — free SPF lookup and check.
Free DMARC record checker — look up and explain a domain’s DMARC policy, instantly.
Check whether a DNS change has propagated across major public resolvers.
Look up domain registration details — registrar, creation date, and expiry.
Check whether an IP address or domain is listed on major spam blacklists (DNSBLs).
Free SSL certificate checker — see when a domain’s certificate expires, and who issued it.
Free HTTP header inspector — see a URL’s response headers, security headers, and caching behavior.
Browse all 152 tools, or use the search box on the homepage to find a specific one.