Create and configure Azure App Service

📘Microsoft Certified: Azure Administrator Associate (AZ-104)

When you create a web app in Azure App Service, it automatically gets a default domain name like:

yourwebapp.azurewebsites.net

While this works for testing, it is not suitable for production, because companies want to use their own domain such as:

www.companyname.com
api.companyname.com
portal.companyname.net

To use your own custom domain, you must map the domain to your App Service. This is called mapping custom DNS names.

Azure App Service supports three main scenarios:

Root domain (example.com)
Subdomain (www.example.com or app.example.com)
Wildcard domains (*.example.com)

Why Custom DNS Mapping Is Important

In real IT environments:

Organizations host customer-facing websites and applications.
They want users to access the site using their company brand.
They may migrate apps from on-premise servers to Azure but keep existing domain names.
They run multiple environments like prod, dev, test, each with its own subdomain.

Mapping custom DNS names helps ensure seamless access for users without changing how they type URLs.

Requirements Before You Begin

Before you can map a DNS name to an App Service, you must have:

1. A custom domain purchased

You can buy a domain from any domain registrar (GoDaddy, Namecheap, Azure DNS, Google Domains, etc.).

2. App Service plan tier that supports custom domains

Custom domains are supported from the Basic tier and above.
Free and Shared tiers do not support custom domain mappings.

3. Access to your DNS zone

This is where you will add DNS records like:

CNAME record
A record
TXT record

Key DNS Records Used for Mapping

DNS Record Type	Purpose
CNAME	Maps a subdomain (like www) to your App Service URL.
A Record	Maps the root domain (example.com) to App Service’s IP address.
TXT record	Used to verify domain ownership in Azure.
ALIAS/ANAME	Some DNS providers use these instead of A records for root domains.

Azure Domain Verification

Azure requires you to verify domain ownership to prevent someone from pointing your domain to their app.

Verification is done by adding a TXT record or a CNAME record provided by Azure.

Example TXT Record Azure may provide:

asuid.example.com → random-generated-value

How Mapping Works (Step-by-Step)

Azure App Service mapping has two main steps:

Step 1 – Add the Custom Domain in the App Service

In the Azure Portal:

Open your App Service.
Select Custom Domains.
Click Add Custom Domain.
Enter the DNS name you want to use (e.g., www.example.com).
Azure shows required DNS records for verification.

Step 2 – Create DNS Records in Your DNS Zone

Depending on the type of domain you want to map, use the following:

Mapping a Subdomain (Recommended Way)

Example: www.example.com, app.example.com

Use a CNAME record

Sample DNS entry:

Type	Name	Value
CNAME	www	yourwebapp.azurewebsites.net

Why CNAME?

It always follows Azure’s internal IP changes.
It does not require hardcoding an IP address.

After DNS propagation, Azure will let you complete the domain assignment.

Mapping a Root Domain (example.com)

Root domains cannot use CNAME (DNS standard restriction).

So Azure offers two options:

Option 1 – Use an A Record

You will map:

A record → the App Service’s static IP
TXT record → verification

Example:

Type	Name	Value
A	@	20.50.18.12
TXT	@	verification code

Option 2 – Use ALIAS/ANAME (if supported by DNS provider)

Some DNS providers support ALIAS or ANAME records at the root.

They work like CNAME but for the root domain.

After DNS Records Are Added

Once your DNS provider finishes propagating (normally 5 minutes to 1 hour):

Return to the App Service → Custom Domains
Azure will verify the DNS records
Click Add to confirm the custom domain

Your app will now respond to the new domain name.

Adding Multiple Domains

App Service can support multiple custom domains such as:

www.company.com
api.company.com
dev.company.com
company.com

Each domain must be added separately and verified.

Wildcard Domains

You can map a wildcard domain:

*.example.com

This is useful for:

Multi-tenant SaaS applications
Environments with many subdomains
Apps generating dynamic subdomains

To enable wildcard domains, create:

Type	Name	Value
CNAME	*	yourwebapp.azurewebsites.net

Using Azure DNS Instead of External DNS Providers

If you host your DNS zone in Azure DNS, you get:

Faster updates
Better integration with Azure App Service
Complete control in portal or Azure CLI
Easier troubleshooting

AZ-104 exam-wise, know how to:

Create a DNS zone
Create DNS records
Delegate domain from registrar to Azure DNS

Troubleshooting DNS Mapping Issues

1. DNS propagation delay

It can take time for DNS to update.
Use tools like:

nslookup
dig
DNSChecker website

2. Incorrect DNS records

Most mapping failures happen due to wrong:

Name field
Record type
Typo in values

3. Wrong App Service tier

Free/Shared tiers cannot map custom domains.

4. SSL not configured

Mapping a domain does NOT automatically provide HTTPS.
You must configure TLS/SSL certificates separately.

AZ-104 Exam Tips

☑ Know when to use CNAME vs A record
☑ Remember that root domains require A records or ALIAS
☑ Custom domains require Basic tier or higher
☑ Azure requires domain ownership verification (TXT or CNAME)
☑ You must add the custom domain both in DNS and in App Service
☑ Mapping custom domain ≠ enabling HTTPS (SSL setup is separate)
☑ Wildcard domain support is available using CNAME

Summary

Mapping a custom DNS name to Azure App Service lets you use your organization’s domain for your application. You must:

Add your custom domain to App Service
Create the required DNS records (TXT + CNAME or A record)
Verify ownership
Complete the domain assignment

This is an important AZ-104 skill because hosting production applications in Azure always requires custom domain mapping.

Map custom DNS names