Subdomain
A domain that is part of a larger domain, like blog.example.com or api.example.com.
A subdomain is a prefix added to your main domain to create a separate web address. In blog.example.com, "blog" is the subdomain and "example.com" is the parent domain. Subdomains can have their own DNS records, pointing to different servers or services. Common uses include api.example.com for APIs, mail.example.com for email, and staging.example.com for testing. Each subdomain needs its own A, AAAA, or CNAME record in DNS. There is no limit to how many subdomains you can create.
Related terms
See also
Referenced on
- Brute-force defense for wp-login.php
- Complete Guide to DNS Attacks and DNS Security (Prevention, Testing & Mitigation)
- Dangling CNAMEs and Subdomain Takeover Risk Across the Global DNS
- DMARC Record Checker
- DNS Checker Bot & Scanner Documentation
- DNS Hijacking Explained: How Attackers Take Control of Your Domain's Resolution
- DNS Over HTTPS Abuse: How Encrypted DNS Creates Security Blind Spots
- DNS Propagation Checker
- DNS Rebinding Attack: How Browsers Are Tricked Into Bypassing Same-Origin Policy
- DNS Tunneling Attack: How Data Is Smuggled Through Port 53
- DNS Water Torture Attack: How Random Subdomain Floods Overwhelm Nameservers
- DNS Zone Transfer Attack (AXFR): How a Single Query Exposes Your Entire Domain
- DNS Zone Walking at the TLD Level: How Attackers Discover Every Domain in a TLD
- DNS Zone Walking for Subdomain Enumeration: How NSEC Exposes Your Subdomains
- Email Authentication by the Numbers: SPF, DKIM, and DMARC Adoption from 262 Million DNS Records
- Free DNS Lookup Tool
- How Expired Name Servers Become Domain Hijacking Vectors
- How to Report Malware and Botnet Command-and-Control Traffic From an IP Address
- How to Report Phishing Emails and Websites Hosted on an IP Address
- How to Set Up a Custom Domain for Your Email (Google Workspace, Microsoft 365)
- How to Verify DNS Changes After Switching Hosting Providers
- HTTP Security Headers Analyzer & Generator
- NXDOMAIN Attack: How Nonexistent Domain Floods Exhaust DNS Resolvers
- Phantom Domain Attack: How Unresponsive Domains Exhaust DNS Resolvers
- Redirect Checker
- Reverse IP Domain Check
- SMTP Diagnostics
- SPF Record Checker
- SPF, DKIM, and DMARC: How DNS Protects Your Email From Spoofing
- Subdomain Takeover: How Dangling DNS Records Let Attackers Hijack Your Domain