All tools

What's My IP

Your public IPv4/IPv6 and the request headers that matter — no third parties involved.

Command-Line IP

Your public IP as plain text — curl checkip.ipcow.com. Force IPv4/IPv6 with -4/-6, or add ?json. Built for scripts.

CIDR Calculator

Network, broadcast, mask, wildcard, host range and counts for any IPv4/IPv6 CIDR.

IP Range → CIDR

Convert an inclusive IP range into the minimal set of CIDR blocks.

IP Geolocation

Approximate location and network (ISP / ASN) for any IP — from self-hosted GeoLite2, never a third-party API.

Network

URL Shortener

Shorten a link on shortcow.com, n9a.us or n48.us — first-party, no tracking, no third-party middlemen.

Ping

ICMP round-trip time to a host, measured from our IPv4 and IPv6 probes.

Port Check

Test whether a TCP port is open and how fast it connects — over IPv4 and IPv6.

HTTP Check

Fetch a URL from our probes and report status, redirects and response time per stack.

HTTP Headers

Fetch a URL, follow the redirect chain, and inspect every response header — with the security headers (HSTS, CSP, X-Frame-Options…) called out.

SMTP Banner

Connect to a mail server and read its SMTP banner — mostly an IPv4 story.

SSL Certificate

Inspect a host's TLS certificate — issuer, validity dates, days to expiry, SANs and chain — over IPv4 and IPv6.

Traceroute

Trace the network path to a host hop by hop — measured from our IPv4 and IPv6 probes.

Diagnostics

Speed Test

Download, upload and latency to our IPv4 and IPv6 servers — no Flash, no ads.

WebSocket Test

Check whether your network allows WebSocket connections — some proxies and firewalls block them.

Sound Test

Play test tones to check your speakers and headphones — left, right and both channels.

Webcam Test

Preview your camera and confirm it works — nothing ever leaves your browser.

DNS

DNS Lookup

Resolve A, AAAA, CNAME, MX, TXT, NS, SOA, CAA or SRV records via Quad9.

Reverse DNS (PTR)

Find the PTR record(s) an IP address resolves back to.

DNSSEC Check

Is the domain DNSSEC-signed and validating? Shows the DNSKEY/DS chain and the resolver's authenticated-data flag.

DNS Propagation

Query a record across Quad9, Cloudflare, Mullvad and AdGuard and see whether they agree — handy after a DNS change.

CAA Check

See which certificate authorities are authorized to issue for a domain.

AAAA Lookup

Resolve a domain's IPv6 (AAAA) address records.

CNAME Lookup

Resolve a host's CNAME alias and the chain it points to.

NS Lookup

List the authoritative nameservers a domain is delegated to.

TXT Lookup

Fetch a domain's TXT records — SPF, verification tokens and free-form text.

SOA Lookup

Read a zone's SOA record — primary NS, contact, serial and refresh/retry/expiry timers.

SRV Lookup

Resolve an SRV service record — priority, weight, port and target host.

DS Lookup

The DS (delegation signer) records that link a zone to its parent in the DNSSEC chain.

DNSKEY Lookup

The DNSKEY records (ZSK/KSK, with key tags) a zone publishes for DNSSEC.

DNS Check

A one-shot overview of a domain's core records (A, AAAA, MX, NS, TXT, SOA, CAA) plus its DNSSEC status.

LOC Lookup

Resolve a DNS LOC record — the latitude, longitude and altitude published for a name.

CERT Lookup

Fetch CERT records — certificates or CRLs stored in DNS (PKIX, PGP, SPKI…).

IPSECKEY Lookup

Resolve IPSECKEY records — the IPsec public key and gateway published for a host.

RRSIG Lookup

The RRSIG signatures over a name — each DNSSEC signature, its validity window and signer.

NSEC Lookup

The NSEC record — the authenticated next name and the record types that exist (DNSSEC).

NSEC3PARAM Lookup

The NSEC3PARAM record — the hash, iterations and salt for a zone’s NSEC3 chain (DNSSEC).

Email

Blacklist Check

Sweep an IP across a curated set of major DNS blacklists (RBLs) at once — see exactly which ones list it.

MX Lookup

List a domain’s mail exchangers in preference order.

SPF Check

Parse SPF and count DNS lookups against the RFC 7208 limit of 10 — the one that catches everyone.

DMARC Check

Resolve and validate the DMARC policy at _dmarc.<domain>.

DKIM Lookup

Fetch a DKIM public key by selector and flag weak keys.

MTA-STS Check

A domain's SMTP TLS posture — the MTA-STS policy (mode, MX, max_age) and the TLS-RPT reporting record.

BIMI Lookup

Find a domain's BIMI brand-logo record and its Verified Mark Certificate (VMC).