Tutorial: Map an existing custom DNS name to Azure App Service

• 06/06/2019
• 12 minutes to read
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Azure App Service provides a highly scalable, self-patching web hosting service. This tutorial shows you how to map an existing custom DNS name to Azure App Service.

In this tutorial, you learn how to:

Prerequisites

To complete this tutorial:

• Create an App Service app, or use an app that you created for another tutorial.

• Purchase a domain name and make sure you have access to the DNS registry for your domain provider (such as GoDaddy).

  For example, to add DNS entries for contoso.com and www.contoso.com, you must be able to configure the DNS settings for the contoso.com root domain.

  Note

  If you don't have an existing domain name, consider purchasing a domain using the Azure portal.

Prepare the app

To map a custom DNS name to a web app, the web app's App Service plan must be a paid tier (Shared, Basic, Standard, Premium or Consumption for Azure Functions). In this step, you make sure that the App Service app is in the supported pricing tier.

Sign in to Azure

Open the Azure portal and sign in with your Azure account.

Select the app in the Azure portal

Search for and select App Services.

On the App Services page, select the name of your Azure app.

You see the management page of the App Service app.

Check the pricing tier

In the left navigation of the app page, scroll to the Settings section and select Scale up (App Service plan).

The app's current tier is highlighted by a blue border. Check to make sure that the app is not in the F1 tier. Custom DNS is not supported in the F1 tier.

If the App Service plan is not in the F1 tier, close the Scale up page and skip to Map a CNAME record.

Scale up the App Service plan

Select any of the non-free tiers (D1, B1, B2, B3, or any tier in the Production category). For additional options, click See additional options.

Click Apply.

When you see the following notification, the scale operation is complete.

Map your domain

You can use either a CNAME record or an A record to map a custom DNS name to App Service. Follow the respective steps:

• Map a CNAME record
• Map an A record
• Map a wildcard domain (with a CNAME record)

Map a CNAME record

In the tutorial example, you add a CNAME record for the www subdomain (for example, www.contoso.com).

Access DNS records with domain provider

Sign in to the website of your domain provider.

Find the page for managing DNS records. Every domain provider has its own DNS records interface, so consult the provider's documentation. Look for areas of the site labeled Domain Name, DNS, or Name Server Management.

Often, you can find the DNS records page by viewing your account information, and then looking for a link such as My domains. Go to that page and then look for a link that is named something like Zone file, DNS Records, or Advanced configuration.

The following screenshot is an example of a DNS records page:

In the example screenshot, you select Add to create a record. Some providers have different links to add different record types. Again, consult the provider's documentation.

Create the CNAME record

Add a CNAME record to map a subdomain to the app's default domain name (<app_name>.azurewebsites.net, where <app_name> is the name of your app).

For the www.contoso.com domain example, add a CNAME record that maps the name www to <app_name>.azurewebsites.net.

After you add the CNAME, the DNS records page looks like the following example:

Enable the CNAME record mapping in Azure

In the left navigation of the app page in the Azure portal, select Custom domains.

In the Custom domains page of the app, add the fully qualified custom DNS name (www.contoso.com) to the list.

Select the + icon next to Add custom domain.

Type the fully qualified domain name that you added a CNAME record for, such as www.contoso.com.

Select Validate.

The Add custom domain page is shown.

Make sure that Hostname record type is set to CNAME (www.example.com or any subdomain).

Select Add custom domain.

It might take some time for the new custom domain to be reflected in the app's Custom domains page. Try refreshing the browser to update the data.

If you missed a step or made a typo somewhere earlier, you see a verification error at the bottom of the page.

Map an A record

In the tutorial example, you add an A record for the root domain (for example, contoso.com).

Copy the app's IP address

To map an A record, you need the app's external IP address. You can find this IP address in the app's Custom domains page in the Azure portal.

In the left navigation of the app page in the Azure portal, select Custom domains.

In the Custom domains page, copy the app's IP address.

Access DNS records with domain provider

Sign in to the website of your domain provider.

Find the page for managing DNS records. Every domain provider has its own DNS records interface, so consult the provider's documentation. Look for areas of the site labeled Domain Name, DNS, or Name Server Management.

Often, you can find the DNS records page by viewing your account information, and then looking for a link such as My domains. Go to that page and then look for a link that is named something like Zone file, DNS Records, or Advanced configuration.

The following screenshot is an example of a DNS records page:

In the example screenshot, you select Add to create a record. Some providers have different links to add different record types. Again, consult the provider's documentation.

Create the A record

To map an A record to an app, App Service requires two DNS records:

• An A record to map to the app's IP address.
• A TXT record to map to the app's default domain name <app_name>.azurewebsites.net. App Service uses this record only at configuration time, to verify that you own the custom domain. After your custom domain is validated and configured in App Service, you can delete this TXT record.

For the contoso.com domain example, create the A and TXT records according to the following table (@ typically represents the root domain).

When the records are added, the DNS records page looks like the following example:

Enable the A record mapping in the app

Back in the app's Custom domains page in the Azure portal, add the fully qualified custom DNS name (for example, contoso.com) to the list.

Select the + icon next to Add custom domain.

Type the fully qualified domain name that you configured the A record for, such as contoso.com.

Select Validate.

The Add custom domain page is shown.

Make sure that Hostname record type is set to A record (example.com).

Select Add custom domain.

It might take some time for the new custom domain to be reflected in the app's Custom domains page. Try refreshing the browser to update the data.

If you missed a step or made a typo somewhere earlier, you see a verification error at the bottom of the page.

Map a wildcard domain

In the tutorial example, you map a wildcard DNS name (for example, *.contoso.com) to the App Service app by adding a CNAME record.

Access DNS records with domain provider

Sign in to the website of your domain provider.

Find the page for managing DNS records. Every domain provider has its own DNS records interface, so consult the provider's documentation. Look for areas of the site labeled Domain Name, DNS, or Name Server Management.

Often, you can find the DNS records page by viewing your account information, and then looking for a link such as My domains. Go to that page and then look for a link that is named something like Zone file, DNS Records, or Advanced configuration.

The following screenshot is an example of a DNS records page:

In the example screenshot, you select Add to create a record. Some providers have different links to add different record types. Again, consult the provider's documentation.

Create the CNAME record

Add a CNAME record to map a wildcard name to the app's default domain name (<app_name>.azurewebsites.net).

For the *.contoso.com domain example, the CNAME record will map the name * to <app_name>.azurewebsites.net.

When the CNAME is added, the DNS records page looks like the following example:

Enable the CNAME record mapping in the app

You can now add any subdomain that matches the wildcard name to the app (for example, sub1.contoso.com and sub2.contoso.com match *.contoso.com).

In the left navigation of the app page in the Azure portal, select Custom domains.

Select the + icon next to Add custom domain.

Type a fully qualified domain name that matches the wildcard domain (for example, sub1.contoso.com), and then select Validate.

The Add custom domain button is activated.

Make sure that Hostname record type is set to CNAME record (www.example.com or any subdomain).

Select Add custom domain.

It might take some time for the new custom domain to be reflected in the app's Custom domains page. Try refreshing the browser to update the data.

Select the + icon again to add another custom domain that matches the wildcard domain. For example, add sub2.contoso.com.

Test in browser

Browse to the DNS name(s) that you configured earlier (for example, contoso.com, www.contoso.com, sub1.contoso.com, and sub2.contoso.com).

Resolve 404 “Not Found”

If you receive an HTTP 404 (Not Found) error when browsing to the URL of your custom domain, verify that your domain resolves to your app's IP address using WhatsmyDNS.net. If not, it may be due to one of the following reasons:

• The custom domain configured is missing an A record and/or a CNAME record.
• The browser client has cached the old IP address of your domain. Clear the cache and test DNS resolution again. On a Windows machine, you clear the cache with ipconfig /flushdns.

Migrate an active domain

To migrate a live site and its DNS domain name to App Service with no downtime, see Migrate an active DNS name to Azure App Service.

Redirect to a custom directory

By default, App Service directs web requests to the root directory of your app code. However, certain web frameworks don't start in the root directory. For example, Laravel starts in the public subdirectory. To continue the contoso.com DNS example, such an app would be accessible at http://contoso.com/public, but you would really want to direct http://contoso.com to the public directory instead. This step doesn't involve DNS resolution, but customizing the virtual directory.

To do this, select Application settings in the left-hand navigation of your web app page.

At the bottom of the page, the root virtual directory / points to site\wwwroot by default, which is the root directory of your app code. Change it to point to the site\wwwroot\public instead, for example, and save your changes.

Once the operation completes, your app should return the right page at the root path (for example, http://contoso.com).

Automate with scripts

You can automate management of custom domains with scripts, using the Azure CLI or Azure PowerShell.

Azure CLI

The following command adds a configured custom DNS name to an App Service app.

az webapp config hostname add \
    --webapp-name <app_name> \
    --resource-group <resource_group_name> \
    --hostname <fully_qualified_domain_name>

For more information, see Map a custom domain to a web app.

Azure PowerShell

The following command adds a configured custom DNS name to an App Service app.

Set-AzWebApp `
    -Name <app_name> `
    -ResourceGroupName <resource_group_name> ` 
    -HostNames @("<fully_qualified_domain_name>","<app_name>.azurewebsites.net")

For more information, see Assign a custom domain to a web app.

Next steps

In this tutorial, you learned how to:

Advance to the next tutorial to learn how to bind a custom SSL certificate to a web app.