Wildcard vs Multi-Domain: Core Differences
| Feature | Wildcard Certificate (*.example.com) | Multi-Domain SAN Certificate |
|---|---|---|
| Coverage | All first-level subdomains dynamically (app.example.com, api.example.com) |
Explicit list of discrete domain names & subdomains |
| Multi-Level Subdomains | ✕ No (does not cover sub.app.example.com) |
✓ Yes (can list explicit deep subdomains) |
| ACME Challenge Method | Requires DNS-01 challenge (API access to DNS provider) | Supports HTTP-01 (port 80 web root) or DNS-01 |
| Private Key Blast Radius | High: If one server is breached, all subdomains are compromised | Low: Each server can have isolated unique key pairs |
Security Recommendation for 2025
For microservice architectures and distributed cloud applications, isolated individual certificates with explicit SANs are recommended over sharing a single wildcard private key across dozens of servers.
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