Network Lookup
the internet, made legible.
IP addresses, ASNs, DNS records, WHOIS data — everything you need to understand what's happening on the network, in one place.
Everything you need
to read the network.
Every tool here runs in the browser or against public registries, with no account and no cost. Each one answers a specific question about a network: who owns this address, is this mail domain configured correctly, what is listening on this port, which manufacturer made this device.
// IP & NETWORK
IP Lookup
Geolocate any IPv4 or IPv6 address. See city, region, country, ISP, ASN, timezone, and coordinates.
Bulk IP Lookup
Paste up to 100 IPs and get geolocation and ASN for all of them at once, with reverse DNS for the first ten. Sortable table, country & ASN summaries, CSV / JSON export.
ASN Explorer
Look up a researched Autonomous System number. Announced prefixes, peer relationships, and routing history.
CIDR Calculator
Calculate subnets for IPv4 and IPv6. Includes VLSM for variable-length subnetting and a complete prefix-length cheat sheet.
Port Lookup
Look up any port number. Assigned service, protocol, security notes, and related ports.
MAC Address Lookup
Identify the device manufacturer from any MAC address: 39k+ IEEE OUI registry entries bundled, plus a directory of researched vendor profiles.
Response Time Checker
HTTP-layer ping from Cloudflare's edge. Sequential probes with TTFB, status codes, jitter, and packet loss for any domain or URL.
Reverse DNS Lookup
PTR lookup for any IPv4 or IPv6 address. With automatic forward-confirmation (FCrDNS), the check mail servers and security tools rely on.
IP Infrastructure Classifier
Infrastructure & risk classification. Our own datacenter/residential ASN analysis + Tor exit detection. Each source labelled, no opaque composite.
IOC Enrichment
One-shot intel report for any IP: infrastructure / risk classification (ASN + Tor), curated DNSBL summary, and reverse DNS. Orchestrated from our own endpoints, each source attributed.
// DNS & DOMAINS
Domain Health Report
One-shot domain check: DNS, SPF/DKIM/DMARC, DNSSEC, SSL/TLS, WHOIS. Each section sourced from our own tools, per-section status.
DNS Records
Resolve A, AAAA, MX, TXT, CNAME, NS, and SOA records for any hostname in real time.
DNS Propagation
Check whether DNS changes have reached 8 public resolvers worldwide — Cloudflare, Google, NextDNS, AliDNS, DNSPod, and more.
DNSSEC Validator
Verify a domain's DNSSEC chain of trust — DS, DNSKEY, RRSIG, and NSEC/NSEC3 records, with key tag matching and algorithm strength.
CAA Record Lookup
See which Certificate Authorities are authorised to issue SSL/TLS certificates for a domain. Walks parent domains per RFC 8659.
Certificate Transparency Search
Discover every subdomain via CT log search. Every SSL certificate ever issued for a domain, deduplicated and ranked by date with issuer breakdown.
Subdomain Finder
Find a domain's subdomains from public TLS certificates in Certificate Transparency logs. Passive, deduped, free. Copy or download the list.
WHOIS & reverse DNS
Query registration, ownership, and contact records for any domain or IP block, and resolve PTR records for reverse DNS.
Typosquatting Checker
Generate lookalike permutations (typos, homoglyphs, TLD swaps, combosquats) for a domain and DoH-check which ones actually resolve.
SPF Record Checker
Look up and validate any domain's SPF record. See every include chain, count DNS lookups, and catch misconfigurations.
DKIM Record Lookup
Look up DKIM signing keys for any domain. Auto-probes 50+ common selectors (Google, Microsoft 365, SES, SendGrid…) and flags weak or revoked keys.
DMARC Record Checker
Look up and validate any domain's DMARC policy. See who receives reports, what happens to failing messages, and an A-F grade.
BIMI Record Lookup
Check if a domain has BIMI configured. The brand logo that appears next to email in Gmail, Apple Mail and Yahoo. Verifies logo, DMARC, VMC status.
MTA-STS & TLS-RPT
Check if a domain enforces encrypted email delivery via MTA-STS. Verifies policy mode, MX coverage, and TLS failure reporting (TLS-RPT).
Email Header Analyzer
Paste raw email headers to trace the message route hop-by-hop, verify SPF/DKIM/DMARC, and locate the origin server. Runs in your browser.
Email Validator
Validate any email. Syntax, MX records, 121k disposable providers, SPF and DMARC posture, and a "did you mean gmail.com?" typo check. Verdict + score.
IP Blacklist Check
Scan any IPv4 address against the major DNSBLs (SpamCop and other commercial-OK lists) in parallel and see exactly which lists flag it.
SPF Record Generator
Build a valid SPF TXT record from a guided form — Google Workspace, Microsoft 365, SendGrid presets, IP allow-list, recommended ~all policy. Client-side.
DMARC Record Generator
Build a valid DMARC TXT record live. Start at p=none for safe monitoring, then move to quarantine or reject. Rua/ruf, pct, alignment, all explained. Client-side.
// WEB SECURITY
SSL Inspector
Check TLS certificates with a security grade from A+ to F. Validity, issuer chain, SANs, HSTS status, and concrete recommendations.
Security Headers Check
Fetch any URL's HTTP response headers and get an A+ → F security grade with CSP analysis and HSTS preload check.
HSTS Preload Checker
Check whether a domain enforces HTTPS via HSTS and qualifies for the browser preload list. Parses the header, checks Chrome's preload requirements.
CSP Analyzer
Analyze any Content Security Policy. Check a URL or paste a CSP string. Grade A+ to F, directive breakdown, weakness detection, fix recommendations.
// PRIVACY & DETECTION
VPN & proxy check
Detect whether an IP belongs to a known VPN, proxy, Tor exit node, or data centre. Check your own apparent identity.
WebRTC Leak Test
Check whether your browser leaks your real IP address through WebRTC. Even if you're on a VPN.
Browser fingerprint
See what your browser reveals without cookies. User agent, screen size, timezone, WebGL renderer, and a uniqueness score.
What's My User Agent?
See your browser's User-Agent string instantly. Parsed into browser, OS, device, engine, plus Client Hints. Runs entirely in your browser.
DNS Leak Test
Check whether your DNS queries leak outside your VPN tunnel. Compares your connection ASN against the resolver that public DoH endpoints see when answering for you.
// DEVELOPER TOOLS
JWT Decoder
Paste a JSON Web Token to decode its header and payload claims (exp, iat, iss, sub) in your browser. Decode-only. Never verifies or signs.
Base64 Encode / Decode
Two-way Base64 with proper UTF-8 handling and an optional URL-safe variant (-/_ alphabet, padding strip). Runs entirely in the browser.
Hash Generator
MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes of text via the Web Crypto API. Honest about which are still secure (and which aren't).
What this site is for.
Network Lookup is a set of free diagnostic tools for the plumbing of the internet: IP addresses, autonomous systems, DNS records, mail authentication, TLS certificates, and the hardware identifiers that show up in device logs. It exists because these lookups are normally scattered across a dozen different sites. Half of them want an account before they will answer a question a registry can resolve in a millisecond.
Nothing here requires signing in, and no tool charges for a result. Where a lookup can be done entirely in your browser, it is: the CIDR calculator, encoders, and token decoders never send your input anywhere. Where an answer has to come from a registry or a live DNS query, the request is made server-side and the source is named on the page.
Who this is for
Mostly people troubleshooting something specific. A sysadmin working out which device on the network has an unfamiliar MAC address. Someone setting up SPF and DMARC for a domain and needing to know whether the records actually parse. An analyst tracing an address in a log back to the network that announced it. The tools assume you know why you are asking, and try to answer without a wall of preamble.
Where the data comes from
Registry data comes from the organisations that maintain it: the five regional internet registries for address and AS allocations, IANA for port assignments, and the IEEE for hardware identifiers. DNS answers come from live queries at lookup time. Every page names its sources, and the sources page lists them together with the licence each one is used under.
We also research and write up individual entries rather than auto-generating a page per record. The ASN directory and the MAC vendor directory list what has been researched so far, and an entry appears only once there is something substantive to say about it.
Reading further
The blog covers the concepts behind the tools at more length: how autonomous systems route traffic, what TCP and UDP actually differ on, and how email authentication fits together. If you want to know more about who runs this and how it is put together, the about page covers it.
Most of what this site knows is not behind a form. Every researched network, port and hardware vendor has a permanent page you can link to, cite, or hand to someone else. A few to see what a finished entry looks like: