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If your website runs multiple subdomains — shop.example.com, mail.example.com, blog.example.com — buying individual SSL certificates for each is expensive and time-consuming. A Wildcard SSL Certificate solves this by securing every subdomain under your domain with a single certificate.
What Is a Wildcard SSL Certificate?
A Wildcard SSL Certificate is an SSL/TLS certificate issued for *.example.com, where the asterisk (*) acts as a placeholder that matches any subdomain name at the same level.
For example, a Wildcard SSL for *.asiagb.com covers:
www.asiagb.comshop.asiagb.commail.asiagb.comblog.asiagb.comapi.asiagb.com- Any other first-level subdomain
Wildcard SSL covers one subdomain level only. For example, *.example.com covers a.example.com but NOT a.b.example.com (two levels deep).
How Wildcard SSL Works
A Wildcard certificate uses the standard X.509 format — the only difference is that the Common Name (CN) and Subject Alternative Name (SAN) fields contain *.example.com instead of a specific hostname.
When a browser connects to shop.example.com, the server presents the certificate with CN = *.example.com. The browser validates that shop matches the wildcard pattern * and accepts the connection as secure.
RFC 2818 Standard
Per RFC 2818, the * character in a Wildcard matches any character except . (dot), which is why it only covers one subdomain level.
Wildcard SSL vs Single-Domain SSL — Comparison
| Feature | Single-Domain SSL | Wildcard SSL | Multi-Domain (SAN) SSL |
|---|---|---|---|
| Coverage | 1 domain | All first-level subdomains | Multiple explicitly listed domains |
| Starting Price (AsiaGB) | 1,000 THB/yr | 5,000 THB/yr | Depends on SAN count |
| Adding new subdomains | Buy a new certificate | No action needed | Must reissue certificate |
| Management complexity | Low (but multiple certs) | Very low | Medium |
| Best for | Single website | Multiple subdomains, one domain | Multiple different domains |
Types of Wildcard SSL Certificates
Wildcard certificates come in two main validation levels:
1. Wildcard DV (Domain Validation)
Validates only domain ownership. Issued within minutes. Suitable for blogs, general websites, and smaller e-commerce stores.
- RapidSSL Wildcard — 5,000 THB/yr · Fast issuance · $10,000 warranty
- GeoTrust QuickSSL Premium Wildcard — 7,000 THB/yr · Global CA · $100,000 warranty
2. Wildcard OV (Organization Validation)
Validates both domain and organization. Takes 1–3 business days but provides higher trust. The certificate displays your organization name.
- GeoTrust True BusinessID Wildcard — 15,000 THB/yr · $1,250,000 warranty
Note: There is no Wildcard EV (Extended Validation) certificate available. EV certificates require explicit domain names and cannot use the * wildcard per CA/Browser Forum standards.
Wildcard SSL Pricing at AsiaGB
| Certificate | Type | Price (1 year) | Warranty |
|---|---|---|---|
| RapidSSL Wildcard | DV Wildcard | 5,000 THB | $10,000 |
| GeoTrust QuickSSL Premium Wildcard | DV Wildcard | 7,000 THB | $100,000 |
| GeoTrust True BusinessID Wildcard | OV Wildcard | 15,000 THB | $1,250,000 |
For most websites and e-commerce stores with multiple subdomains, RapidSSL Wildcard at 5,000 THB/yr offers the best value. If you need higher trust signals for your customers, consider the GeoTrust Wildcard.
Installing Wildcard SSL on DirectAdmin
After purchasing your Wildcard SSL and receiving the certificate from the CA, follow these steps:
Step 1: Generate a CSR
Log in to DirectAdmin → SSL Certificates → Select Create a Certificate Request
- In the Common Name field, enter:
*.example.com(include the asterisk) - Fill in all organization details
- Click Save — the system generates your Private Key and CSR
Step 2: Submit CSR to the CA
Copy the generated CSR and submit it to the CA through billing.in.th. Once the CA approves it, they will send back your Certificate file (.crt or .pem).
Step 3: Install the Certificate
Return to DirectAdmin → SSL Certificates → Choose Paste a pre-generated certificate and key
- Paste the Private Key in the Key field
- Paste the Certificate in the Certificate field
- If the CA provided an Intermediate CA bundle, paste it in the CA Certificate field
- Click Save
Step 4: Verify
Open your browser and navigate to any subdomain, e.g. https://shop.example.com. You should see a padlock icon and the correct domain name.
# Verify SSL from the command line
openssl s_client -connect shop.example.com:443 -servername shop.example.com 2>/dev/null | openssl x509 -noout -subject -datesWildcard SSL vs Let's Encrypt — Key Differences
Let's Encrypt issues Wildcard certificates for free via the ACME protocol, but there are important trade-offs to understand:
| Aspect | Let's Encrypt Wildcard | Commercial Wildcard (AsiaGB) |
|---|---|---|
| Cost | Free | 5,000–15,000 THB/yr |
| Certificate validity | 90 days | 1 year |
| Renewal | Manual / automated script | Email reminders, assisted renewal |
| DNS-01 challenge required | Yes (for Wildcard) | No |
| Warranty | None | $10,000–$1,250,000 |
| Support | Community only | AsiaGB team support |
Let's Encrypt suits developers who are comfortable with automation. Commercial Wildcards are better for business websites that need a warranty, SLA, and expert support.
Pre-Purchase Checklist
- ✅ You have more than 2 subdomains (if only 1, single-domain SSL is cheaper)
- ✅ All subdomains are under the same root domain
- ✅ No subdomain is deeper than one level (e.g.
a.b.example.com) - ✅ You have DNS management access for the domain
- ✅ Your hosting supports custom SSL installation (DirectAdmin supports all plans)
- ✅ You have a plan for certificate renewal before expiry
Frequently Asked Questions
*.example.com) covers all subdomains at a single level — mail.example.com, shop.example.com, etc. — but does NOT cover second-level subdomains like sub.sub.example.com.example.com). A Wildcard SSL secures every subdomain at the first level under your root domain (*.example.com), so one certificate handles mail, shop, blog, api, and more.www.example.com is a subdomain of example.com, so *.example.com covers it. Most CAs issue the certificate with both example.com (root) and *.example.com included automatically.Summary — Who Needs Wildcard SSL?
Wildcard SSL is the ideal choice for any website running multiple subdomains under a single domain: e-commerce stores with shop, api, cdn; corporate portals with mail, hr, support; or SaaS platforms with per-customer subdomains.
Cost comparison: buying 3 separate SSLs costs 3,000 THB, while RapidSSL Wildcard is 5,000 THB. But with 6 subdomains, Wildcard is clearly cheaper — and you never need to worry about adding new subdomains.
AsiaGB offers several Wildcard SSL options to match your budget, backed by a team that can assist with installation on DirectAdmin around the clock. Uptime 99% guaranteed.