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11 tools
WHOIS LookupDomain Age CheckerSubdomain FinderIP GeolocationASN / BGP LookupIP Blacklist CheckReverse IP LookupMAC Address LookupBGP Prefix LookupRPKI / ROA CheckDomain Availability
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What Is My IP?IPv6 TestSpeed TestHTTP Request Headers
DNS LookupDNS PropagationDNS Health CheckerSPF AnalyzerPTR LookupCAA RecordSRV RecordDNS TraceDNS PrivacyDANE / TLSADNSSEC CheckerSPF BuilderDKIM GeneratorZone DiffPTR Zone Generator
Subnet CalculatorCIDR Range ViewerVLSM CalculatorVLAN PlannerBandwidth CalcIPv6 Subnet CalcIP ↔ BinarySupernet CalcCIDR MergeCIDR to IP RangeCIDR SplitIPv4 → IPv6CIDR OverlapFree IP Space FinderDHCP CalculatorMTU Calculator
WHOIS LookupDomain Age CheckerSubdomain FinderIP GeolocationASN / BGP LookupIP Blacklist CheckReverse IP LookupMAC Address LookupBGP Prefix LookupRPKI / ROA CheckDomain Availability
Email InspectorDKIM CheckerEmail HeadersSMTP Test
SMTP TLS CheckSoon
MX Health CheckEmail SecurityDMARC Generator
Temp MailSoon
Is It Down?SSL/TLS CheckerOpen Port CheckerOG Tag CheckerOCSP CheckerPing / LatencyHTTP InspectorRedirect ChainCSP AnalyzerTech Stack CheckerBetaTracerouteBetaHTTP/2 + HTTP/3robots.txt ViewerSSL Cert DecoderBanner GrabberWebSocket TesterCORS TesterHTTP TimingStructured DataPWA ManifestSEO Auditor
One-Time SecretHash GeneratorPassword StrengthSecurity.txtCT Log SearchAXFR Zone Test
HTTP Sec ScoreSoon
WebRTC Leak TestIP Reputation
JSON FormatterYAML FormatterBase64 / URL EncodeJWT DecoderRegex TesterUnix TimestampCron BuilderUUID / ULIDPunycode / IDNBase ConverterACL Generator
CSS Unit ConverterColor ToolkitGradient GeneratorcURL BuilderURL ParserURL Encoder/DecoderHTTP Status CodesBox Shadow GenFavicon GeneratorQR Code GeneratorFlex & Gridrobots.txt Tester
Text CompareCase ConverterText CleanerText AnalyzerText TransformerList ToolsLorem GeneratorSlug Generator
Cloud VPC PlannerCloud IP RangeSecurity GroupsIAM AnalyzerK8s CIDR PlannerFirewall BuilderHCL FormatterEgress Cost CalcCloud DNS Zone
VM Cost EstimatorSoon
Proxmox Net ConfigVMware Port GroupHyper-V vSwitchVXLAN VNI PlannerKVM Net ConfigXCP-ng NetworkNSX-T Segment
Disposable Email DetectorPhone InspectorTor Exit NodeVPN/Proxy DetectDomain ReputationTyposquat DetectUsername SearchFavicon Hash
GitHub ActionsDockerfile Gendocker-composeArgoCD AppK8s Manifests
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2.63.a76559e

Subdomain Finder

Find subdomains by searching public Certificate Transparency logs. Results include all subdomains that have ever had an HTTPS certificate issued.

Examples:

Enter a domain to discover its subdomains via Certificate Transparency logs

Related Tools

DNS Lookup

Query any DNS record type for any domain - A, AAAA, MX, TXT, CNAME, NS, SOA, CAA. Results come from our own neutral resolver.

WHOIS Lookup

Look up domain registration details - registrar, expiry date, nameservers, and status. Data comes from the RDAP protocol, the modern successor to classic WHOIS.

Domain Age Checker

Check how old a domain is and when it expires. Uses WHOIS/RDAP registration data.

About this tool

Certificate Transparency (CT) is a public, append-only ledger of every TLS/SSL certificate ever issued by participating Certificate Authorities. Since certificates include the domain names they cover, CT logs are a comprehensive source of subdomain enumeration - no active scanning required. This tool queries the Certificate Transparency database via CertSpotter, which indexes CT logs from all major CAs including Let's Encrypt, DigiCert, and Sectigo. When CertSpotter does not answer, the tool asks crt.sh, another CT log search. The addresses and mail servers of the subdomains found are then looked up through Cloudflare DNS, with VLANlab's own resolver when Cloudflare does not answer.

Results include subdomains that are no longer active, wildcard certificates are excluded (a cert for *.example.com does not reveal specific subdomains), and subdomains only reachable over HTTP (no HTTPS) will not appear. Results are based on the most recent 1,000 certificates and are cached for 1 hour.