With SQL Server backup to URL, you specify an Azure blob storage container as the destination for your full, differential, and transaction log backups, and you manage the backup process and the retention strategy. A primary reason to use SQL Server backup to URL is to avoid the cost of backing up to attached disks that use premium storage (although you always can back up to attached premium storage for performance and then archive to blob storage).
To use this backup mechanism, take the following steps:
Create an Azure storage account.
Create a container within the storage account to contain your backup files.
Generate a Shared Access policy and apply the Shared Access Signature (SAS) token to the Azure blob container.
Create a SQL Server credential based on the SAS token.
Specify TO URL as an argument with your BACKUP DATABASE and BACKUP LOG commands.
BACKUP DATABASE AdventureWorks2016 TO URL = 'https://
Backup to URL is a strategy you will want to use to save money when your Azure virtual machine is using premium storage because SQL Server backup to URL uses standard storage. The maximum size for a single file using a SAS token is 200 GB, and the maximum backup size using a striped backup set is 12.8 terabytes (TB).
Note You can back up to a single backup with a maximum size of 1 TB using the legacy SQL Server 2014 syntax of WITH CREDENTIAL that utilizes the storage account access key rather than a SAS key. This syntax is being deprecated.
Source of Information : Migrating SQL Server Databases to Azure