add verification ID

Author: cephalin

articles/app-service/app-service-web-tutorial-custom-domain.md

@@ -6,7 +6,7 @@ keywords: app service, azure app service, domain mapping, domain name, existing
 ms.assetid: dc446e0e-0958-48ea-8d99-441d2b947a7c
 ms.devlang: nodejs
 ms.topic: tutorial
-ms.date: 06/06/2019
+ms.date: 04/27/2020
 ms.custom: mvc, seodec18
 ---
 
@@ -89,6 +89,12 @@ When you see the following notification, the scale operation is complete.
 
 <a name="cname" aria-hidden="true"></a>
 
+## Get domain verification ID
+
+To add a custom domain to your app, you need to verify your ownership of the domain by adding a verification ID as a TXT record with your domain provider. In the left navigation of your app page, click **Resource explorer** under **Development Tools**, then click **Go**.
+
+In the JSON view of your app's properties, search for `customDomainVerificationId`, and copy its value inside the double quotes. You need this verification ID for the next step.
+
 ## 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:
@@ -110,11 +116,14 @@ In the tutorial example, you add a CNAME record for the `www` subdomain (for exa
 
 #### 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).
+Map a subdomain to the app's default domain name (`<app_name>.azurewebsites.net`, where `<app_name>` is the name of your app). To create a CNAME mapping for the `www` subdomain, create two records:
 
-For the `www.contoso.com` domain example, add a CNAME record that maps the name `www` to `<app_name>.azurewebsites.net`.
+| Record type | Host | Value | Comments |
+| - | - | - |
+| CNAME | `www` | `<app_name>.azurewebsites.net` | The domain mapping itself. |
+| TXT | `asuid.www` | [The verification ID you got earlier](#get-domain-verification-id) | App Service accesses the `asuid.<subdomain>` TXT record to verify your ownership of the custom domain. |
 
-After you add the CNAME, the DNS records page looks like the following example:
+After you add the CNAME and TXT records, the DNS records page looks like the following example:
 
 ![Portal navigation to Azure app](./media/app-service-web-tutorial-custom-domain/cname-record.png)
 
@@ -179,25 +188,20 @@ In the **Custom domains** page, copy the app's IP address.
 
 #### Create the A record
 
-To map an A record to an app, App Service requires **two** DNS records:
+To map an A record to an app, usually to the root domain, create two 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).
-
-| Record type | Host | Value |
+| Record type | Host | Value | Comments |
 | - | - | - |
-| A | `@` | IP address from [Copy the app's IP address](#info) |
-| TXT | `@` | `<app_name>.azurewebsites.net` |
+| A | `@` | IP address from [Copy the app's IP address](#info) | The domain mapping itself (`@` typically represents the root domain). |
+| TXT | `asuid` | [The verification ID you got earlier](#get-domain-verification-id) | App Service accesses the `asuid.<subdomain>` TXT record to verify your ownership of the custom domain. For the root domain, use `asuid`. |
 
 > [!NOTE]
 > To add a subdomain (like `www.contoso.com`) using an A record instead of a recommended [CNAME record](#map-a-cname-record), your A record and TXT record should look like the following table instead:
 >
 > | Record type | Host | Value |
 > | - | - | - |
 > | A | `www` | IP address from [Copy the app's IP address](#info) |
-> | TXT | `www` | `<app_name>.azurewebsites.net` |
+> | TXT | `asuid.www` | `<app_name>.azurewebsites.net` |
 >
 
 When the records are added, the DNS records page looks like the following example:
@@ -253,6 +257,11 @@ Add a CNAME record to map a wildcard name to the app's default domain name (`<ap
 
 For the `*.contoso.com` domain example, the CNAME record will map the name `*` to `<app_name>.azurewebsites.net`.
 
+| Record type | Host | Value | Comments |
+| - | - | - |
+| CNAME | `*` | `<app_name>.azurewebsites.net` | The domain mapping itself. |
+| TXT | `asuid.<subdomain>` | [The verification ID you got earlier](#get-domain-verification-id) | App Service accesses the `asuid.<subdomain>` TXT record to verify your ownership of the custom domain. |
+
 When the CNAME is added, the DNS records page looks like the following example:
 
 ![Portal navigation to Azure app](./media/app-service-web-tutorial-custom-domain/cname-record-wildcard.png)