Changes in Windows Server AMIs by OS version

• Windows Server 2025 AMIs use UEFI boot mode by default, except for Windows Server 2025 AMIs named BIOS-Windows_Server-2025-English-Full-Base.

  Note

  EC2 metal instance sizes and some EC2 instance types do not support UEFI boot mode for Windows Server. To launch Windows Server 2025 on these instances, you must use the AWS managed BIOS-Windows_Server-2025-English-Full-Base AMI, or an AMI that is based on that image. For more information about UEFI requirements, Requirements for UEFI boot mode in the Amazon EC2 User Guide.

• Windows Server 2025 AMIs support Nitro EC2 instance types only.

• Windows Server 2025 AMIs use gp3 EBS volume types by default.

• Windows Credential Guard is not supported on AWS Windows Server 2025 AMIs.

• To accommodate the change from .NET Framework to .NET Core, the EC2Config service has been deprecated on Windows Server 2016 AMIs and replaced by EC2Launch. EC2Launch is a bundle of Windows PowerShell scripts that perform many of the tasks performed by the EC2Config service. For more information, see Configure a Windows instance using EC2Launch. EC2Launch v2 replaces EC2Launch in Windows Server 2022 and later. For more information, see Configure a Windows instance using EC2Launch v2.

• On earlier versions of Windows Server AMIs, you can use the EC2Config service to join an EC2 instance to a domain and configure integration with Amazon CloudWatch. On Windows Server 2016 and later AMIs, you can use the CloudWatch agent to configure integration with Amazon CloudWatch. For more information about configuring instances to send log data to CloudWatch, see Collect Metrics and Logs from Amazon EC2 Instances and On-Premises Servers with the CloudWatch Agent. For information about joining an EC2 instance to a domain, see Join an Instance to a Domain Using the AWS-JoinDirectoryServiceDomain JSON Document in the AWS Systems Manager User Guide.

Other differences

Note the following additional important differences for instances created from Windows Server 2016 and later AMIs.

• By default, EC2Launch does not initialize secondary EBS volumes. You can configure EC2Launch to initialize disks automatically by either scheduling the script to run or by calling EC2Launch in user data. For the procedure to initialize disks using EC2Launch, see "Initialize Drives and Drive Letter Mappings" in Configure EC2Launch.

• If you previously enabled CloudWatch integration on your instances by using a local configuration file (AWS.EC2.Windows.CloudWatch.json), you can configure the file to work with the SSM Agent on instances created from Windows Server 2016 and later AMIs.