Network Tools

Look up which Autonomous System (ASN) an IP address belongs to, or look up an ASN's registration details directly. Free, fast, no signup.

Check whether a domain or IPv4 address is listed on major DNSBL/RBL spam blacklists like Spamhaus, Barracuda, and SORBS. Free, instant, no signup required.

Check which certificate authorities may issue SSL certificates for a domain. Reads CAA records, including inherited ones, wildcard rules, and iodef.

Check whether a URL's CORS response headers would allow a cross-origin request from your app. Free, fast, no signup.

Look up any country's ISO codes, calling code, and official currency in one searchable reference table. Free, instant, entirely in your browser.

Check whether a domain has a DMARC policy and see its exact contents. Free, fast DMARC record lookup with no signup required.

Look up A, AAAA, CNAME, MX, TXT, NS, and SOA records for any domain. Fast, free DNS record checker with no signup required.

Check a domain's DNS records against several major public resolvers at once to see whether a recent change has propagated. Free, fast, no signup.

Check whether a domain is protected by DNSSEC: DS and DNSKEY records, key tag matching, algorithms, and whether resolvers can validate its answers.

Get a single 0-100 health score for a domain, combining its DNS, SSL certificate, SPF, DMARC, and security-header status in one check.

Find out how old a domain is from its RDAP registration date. Free, instant domain age lookup with no signup required.

Check whether a domain is registered or available via RDAP. Free, instant domain availability check with no signup required.

See the exact HTTP response headers a URL returns, including every redirect hop along the way. Free, fast, no signup.

Check the HTTP status code a URL returns, and trace every redirect hop along the way. Free, fast, no signup.

Look up an IP address's approximate location, timezone, and ISP or hosting provider. Free, fast, no signup.

Look up the hardware manufacturer registered for a MAC address's OUI prefix. Free, fast, no signup.

Look up the MIME type for a file extension, or the extension for a MIME type, from a curated reference of common types. Free and instant in your browser.

Look up a domain's mail exchange (MX) records to see where its email is routed. Free, fast, no signup required.

See exactly which Open Graph and Twitter Card tags a URL serves, the same way a social platform's link unfurler would. Free, fast, no signup.

Find out which registrar a domain is registered through via RDAP. Free, instant registrar lookup with no signup required.

Look up the reverse-DNS (PTR) hostname registered for an IP address. Free, fast, no signup required.

Fetch and parse a site's robots.txt into readable rules — user agents, disallowed paths, and linked sitemaps. Free, fast, no signup.

Check whether a domain has an SPF record and see its exact contents. Free, fast SPF record lookup with no signup required.

Check a domain's SSL/TLS certificate — issuer, expiry date, and validity — by connecting directly on port 443. Free, fast, no signup.

Fetch and structurally validate an XML sitemap — confirms it's well-formed, has the right root element, and every entry has a location. Free, fast, no signup.

Calculate IPv4 and IPv6 subnets from CIDR notation: network, broadcast, host range, masks, and address type, and split a network into smaller subnets.

Browse and search top-level domains, including gTLDs, ccTLDs, and popular new gTLDs, with each registry and a short note. Free and instant in your browser.

Check which TLS protocol versions a domain supports and which one it negotiates by default. Free, fast, no signup.

Break a URL down into its protocol, host, port, path, query string, and fragment. Free, fast, runs entirely in your browser.

Look up a domain's registrar, registration status, key dates, and nameservers via RDAP. Fast, free WHOIS lookup with no signup required.

See your public IP address instantly, with IPv4 or IPv6 version, approximate location, and internet provider, plus your browser and device details.

Look up the postal code format used by any country — pattern, structure, and example. Free, instant, entirely in your browser.

Validate a website’s security.txt against RFC 9116: location, HTTPS, content type, Contact and Expires fields, signature, and common mistakes.