Prerequisites for Azure AD Connect

This article describes the prerequisites and the hardware requirements for Azure Active Directory (Azure AD) Connect.

Before you install Azure AD Connect

Before you install Azure AD Connect, there are a few things that you need.

Azure AD

  • You need an Azure AD tenant. You get one with an Azure free trial. You can use one of the following portals to manage Azure AD Connect:
  • Add and verify the domain you plan to use in Azure AD. For example, if you plan to use for your users, make sure this domain has been verified and you're not using only the default domain.
  • An Azure AD tenant allows, by default, 50,000 objects. When you verify your domain, the limit increases to 300,000 objects. If you need even more objects in Azure AD, open a support case to have the limit increased even further. If you need more than 500,000 objects, you need a license, such as Microsoft 365, Azure AD Premium, or Enterprise Mobility + Security.

Prepare your on-premises data

On-premises Active Directory

  • The Active Directory schema version and forest functional level must be Windows Server 2003 or later. The domain controllers can run any version as long as the schema version and forest-level requirements are met.
  • If you plan to use the feature password writeback, the domain controllers must be on Windows Server 2016 or later.
  • The domain controller used by Azure AD must be writable. Using a read-only domain controller (RODC) isn't supported, and Azure AD Connect doesn't follow any write redirects.
  • Using on-premises forests or domains by using "dotted" (name contains a period ".") NetBIOS names isn't supported.
  • We recommend that you enable the Active Directory recycle bin.

PowerShell execution policy

Azure Active Directory Connect runs signed PowerShell scripts as part of the installation. Ensure that the PowerShell execution policy will allow running of scripts.

The recommended execution policy during installation is "RemoteSigned".

For more information on setting the PowerShell execution policy, see Set-ExecutionPolicy.

Azure AD Connect server

The Azure AD Connect server contains critical identity data. It's important that administrative access to this server is properly secured. Follow the guidelines in Securing privileged access.

The Azure AD Connect server must be treated as a Tier 0 component as documented in the Active Directory administrative tier model

To read more about securing your Active Directory environment, see Best practices for securing Active Directory.

Installation prerequisites

  • Azure AD Connect must be installed on a domain-joined Windows Server 2016 or later.
  • Azure AD Connect can't be installed on Small Business Server or Windows Server Essentials before 2019 (Windows Server Essentials 2019 is supported). The server must be using Windows Server standard or better.
  • The Azure AD Connect server must have a full GUI installed. Installing Azure AD Connect on Windows Server Core isn't supported.
  • The Azure AD Connect server must not have PowerShell Transcription Group Policy enabled if you use the Azure AD Connect wizard to manage Active Directory Federation Services (AD FS) configuration. You can enable PowerShell transcription if you use the Azure AD Connect wizard to manage sync configuration.
  • If AD FS is being deployed:
  • It is not supported to break and analyze traffic between Azure AD Connect and Azure AD. Doing so may disrupt the service.
  • If your global administrators have MFA enabled, the URL must be in the trusted sites list. You're prompted to add this site to the trusted sites list when you're prompted for an MFA challenge and it hasn't been added before. You can use Internet Explorer to add it to your trusted sites.
  • If you plan to use Azure AD Connect Health for syncing, ensure that the prerequisites for Azure AD Connect Health are also met. For more information, see Azure AD Connect Health agent installation.

Harden your Azure AD Connect server

We recommend that you harden your Azure AD Connect server to decrease the security attack surface for this critical component of your IT environment. Following these recommendations will help to mitigate some security risks to your organization.

  • Treat Azure AD Connect the same as a domain controller and other Tier 0 resources. For more information, see Active Directory administrative tier model.
  • Restrict administrative access to the Azure AD Connect server to only domain administrators or other tightly controlled security groups.
  • Create a dedicated account for all personnel with privileged access. Administrators shouldn't be browsing the web, checking their email, and doing day-to-day productivity tasks with highly privileged accounts.
  • Follow the guidance provided in Securing privileged access.
  • Deny use of NTLM authentication with the AADConnect server. Here are some ways to do this: Restricting NTLM on the AADConnect Server and Restricting NTLM on a domain
  • Ensure every machine has a unique local administrator password. For more information, see Local Administrator Password Solution (LAPS) can configure unique random passwords on each workstation and server store them in Active Directory protected by an ACL. Only eligible authorized users can read or request the reset of these local administrator account passwords. You can obtain the LAPS for use on workstations and servers from the Microsoft Download Center. Additional guidance for operating an environment with LAPS and privileged access workstations (PAWs) can be found in Operational standards based on clean source principle.
  • Implement dedicated privileged access workstations for all personnel with privileged access to your organization's information systems.
  • Follow these additional guidelines to reduce the attack surface of your Active Directory environment.
  • Follow the Monitor changes to federation configuration to setup alerts to monitor changes to the trust established between your Idp and Azure AD.
  • Enable Multi Factor Authentication (MFA) for all users that have privileged access in Azure AD or in AD. One security issue with using AADConnect is that if an attacker can get control over the Azure AD Connect server they can manipulate users in Azure AD. To prevent a attacker from using these capabilities to take over Azure AD accounts, MFA offers protections so that even if an attacker manages to e.g. reset a user's password using Azure AD Connect they still cannot bypass the second factor.

SQL Server used by Azure AD Connect

  • Azure AD Connect requires a SQL Server database to store identity data. By default, a SQL Server 2019 Express LocalDB (a light version of SQL Server Express) is installed. SQL Server Express has a 10-GB size limit that enables you to manage approximately 100,000 objects. If you need to manage a higher volume of directory objects, point the installation wizard to a different installation of SQL Server. The type of SQL Server installation can impact the performance of Azure AD Connect.
  • If you use a different installation of SQL Server, these requirements apply:
    • Azure AD Connect supports all versions of SQL Server from 2012 (with the latest service pack) to SQL Server 2019. Azure SQL Database isn't supported as a database.
    • You must use a case-insensitive SQL collation. These collations are identified with a _CI_ in their name. Using a case-sensitive collation identified by _CS_ in their name isn't supported.
    • You can have only one sync engine per SQL instance. Sharing a SQL instance with FIM/MIM Sync, DirSync, or Azure AD Sync isn't supported.


  • You must have an Azure AD Global Administrator account for the Azure AD tenant you want to integrate with. This account must be a school or organization account and can't be a Microsoft account.
  • If you use express settings or upgrade from DirSync, you must have an Enterprise Administrator account for your on-premises Active Directory.
  • If you use the custom settings installation path, you have more options. For more information, see Custom installation settings.


  • The Azure AD Connect server needs DNS resolution for both intranet and internet. The DNS server must be able to resolve names both to your on-premises Active Directory and the Azure AD endpoints.

  • Azure AD Connect requires network connectivity to all configured domains

  • If you have firewalls on your intranet and you need to open ports between the Azure AD Connect servers and your domain controllers, see Azure AD Connect ports for more information.

  • If your proxy or firewall limit which URLs can be accessed, the URLs documented in Office 365 URLs and IP address ranges must be opened. Also see Safelist the Azure portal URLs on your firewall or proxy server.

  • Azure AD Connect (version 1.1.614.0 and after) by default uses TLS 1.2 for encrypting communication between the sync engine and Azure AD. If TLS 1.2 isn't available on the underlying operating system, Azure AD Connect incrementally falls back to older protocols (TLS 1.1 and TLS 1.0). From Azure AD Connect version 2.0 onwards. TLS 1.0 and 1.1 are no longer supported and installation will fail if TLS 1.2 is not enabled.

  • Prior to version 1.1.614.0, Azure AD Connect by default uses TLS 1.0 for encrypting communication between the sync engine and Azure AD. To change to TLS 1.2, follow the steps in Enable TLS 1.2 for Azure AD Connect.

  • If you're using an outbound proxy for connecting to the internet, the following setting in the C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config file must be added for the installation wizard and Azure AD Connect sync to be able to connect to the internet and Azure AD. This text must be entered at the bottom of the file. In this code, <PROXYADDRESS> represents the actual proxy IP address or host name.

  • If your proxy server requires authentication, the service account must be located in the domain. Use the customized settings installation path to specify a custom service account. You also need a different change to machine.config. With this change in machine.config, the installation wizard and sync engine respond to authentication requests from the proxy server. In all installation wizard pages, excluding the Configure page, the signed-in user's credentials are used. On the Configure page at the end of the installation wizard, the context is switched to the service account that you created. The machine.config section should look like this:

            <defaultProxy enabled="true" useDefaultCredentials="true">
  • If the proxy configuration is being done in an existing setup, the Microsoft Azure AD Sync service needs to be restarted once for the Azure AD Connect to read the proxy configuration and update the behavior.

  • When Azure AD Connect sends a web request to Azure AD as part of directory synchronization, Azure AD can take up to 5 minutes to respond. It's common for proxy servers to have connection idle timeout configuration. Ensure the configuration is set to at least 6 minutes or more.

For more information, see MSDN about the default proxy element. For more information when you have problems with connectivity, see Troubleshoot connectivity problems.


Optional: Use a test user account to verify synchronization.

Component prerequisites

PowerShell and .NET Framework

Azure AD Connect depends on Microsoft PowerShell 5.0 and .NET Framework 4.5.1. You need this version or a later version installed on your server.

Enable TLS 1.2 for Azure AD Connect

Prior to version 1.1.614.0, Azure AD Connect by default uses TLS 1.0 for encrypting the communication between the sync engine server and Azure AD. You can configure .NET applications to use TLS 1.2 by default on the server. For more information about TLS 1.2, see Microsoft Security Advisory 2960358.

  1. Make sure you have the .NET 4.5.1 hotfix installed for your operating system. For more information, see Microsoft Security Advisory 2960358. You might have this hotfix or a later release installed on your server already.

  2. For all operating systems, set this registry key and restart the server.

  3. If you also want to enable TLS 1.2 between the sync engine server and a remote SQL Server, make sure you have the required versions installed for TLS 1.2 support for Microsoft SQL Server.

DCOM prerequisites on the synchronization server

During the installation of the synchronization service, Azure AD Connect checks for the presence of the following registry key:

  • HKEY_LOCAL_MACHINE: Software\Microsoft\Ole

Under this registry key, Azure AD Connect will check to see if the following values are present and uncorrupted:

Prerequisites for federation installation and configuration

Windows Remote Management

When you use Azure AD Connect to deploy AD FS or the Web Application Proxy (WAP), check these requirements:

  • If the target server is domain joined, ensure that Windows Remote Managed is enabled.
    • In an elevated PowerShell command window, use the command Enable-PSRemoting –force.
  • If the target server is a non-domain-joined WAP machine, there are a couple of additional requirements:
    • On the target machine (WAP machine):
      • Ensure the Windows Remote Management/WS-Management (WinRM) service is running via the Services snap-in.
      • In an elevated PowerShell command window, use the command Enable-PSRemoting –force.
    • On the machine on which the wizard is running (if the target machine is non-domain joined or is an untrusted domain):
      • In an elevated PowerShell command window, use the command Set-Item.WSMan:\localhost\Client\TrustedHosts –Value <DMZServerFQDN> -Force –Concatenate.
      • In the server manager:
        • Add a DMZ WAP host to a machine pool. In the server manager, select Manage > Add Servers, and then use the DNS tab.
        • On the Server Manager All Servers tab, right-click the WAP server, and select Manage As. Enter local (not domain) credentials for the WAP machine.
        • To validate remote PowerShell connectivity, on the Server Manager All Servers tab, right-click the WAP server and select Windows PowerShell. A remote PowerShell session should open to ensure remote PowerShell sessions can be established.

TLS/SSL certificate requirements

  • We recommend that you use the same TLS/SSL certificate across all nodes of your AD FS farm and all Web Application Proxy servers.
  • The certificate must be an X509 certificate.
  • You can use a self-signed certificate on federation servers in a test lab environment. For a production environment, we recommend that you obtain the certificate from a public certificate authority.
    • If you're using a certificate that isn't publicly trusted, ensure that the certificate installed on each Web Application Proxy server is trusted on both the local server and on all federation servers.
  • The identity of the certificate must match the federation service name (for example,
    • The identity is either a subject alternative name (SAN) extension of type dNSName or, if there are no SAN entries, the subject name is specified as a common name.
    • Multiple SAN entries can be present in the certificate provided one of them matches the federation service name.
    • If you're planning to use Workplace Join, an additional SAN is required with the value enterpriseregistration. followed by the user principal name (UPN) suffix of your organization, for example,
  • Certificates based on CryptoAPI next-generation (CNG) keys and key storage providers (KSPs) aren't supported. As a result, you must use a certificate based on a cryptographic service provider (CSP) and not a KSP.
  • Wild-card certificates are supported.

Name resolution for federation servers

  • Set up DNS records for the AD FS name (for example, for both the intranet (your internal DNS server) and the extranet (public DNS through your domain registrar). For the intranet DNS record, ensure that you use A records and not CNAME records. Using A records is required for Windows authentication to work correctly from your domain-joined machine.
  • If you're deploying more than one AD FS server or Web Application Proxy server, ensure that you've configured your load balancer and that the DNS records for the AD FS name (for example, point to the load balancer.
  • For Windows integrated authentication to work for browser applications using Internet Explorer in your intranet, ensure that the AD FS name (for example, is added to the intranet zone in Internet Explorer. This requirement can be controlled via Group Policy and deployed to all your domain-joined computers.

Azure AD Connect supporting components

Azure AD Connect installs the following components on the server where Azure AD Connect is installed. This list is for a basic Express installation. If you choose to use a different SQL Server on the Install synchronization services page, SQL Express LocalDB isn't installed locally.

  • Azure AD Connect Health
  • Microsoft SQL Server 2019 Command Line Utilities
  • Microsoft SQL Server 2019 Express LocalDB
  • Microsoft SQL Server 2019 Native Client
  • Microsoft Visual C++ 14 Redistribution Package

Hardware requirements for Azure AD Connect

The following table shows the minimum requirements for the Azure AD Connect sync computer.

Number of objects in Active Directory CPU Memory Hard drive size
Fewer than 10,000 1.6 GHz 4 GB 70 GB
10,000–50,000 1.6 GHz 4 GB 70 GB
50,000–100,000 1.6 GHz 16 GB 100 GB
For 100,000 or more objects, the full version of SQL Server is required. For performance reasons, installing locally is preferred.
100,000–300,000 1.6 GHz 32 GB 300 GB
300,000–600,000 1.6 GHz 32 GB 450 GB
More than 600,000 1.6 GHz 32 GB 500 GB

The minimum requirements for computers running AD FS or Web Application Proxy servers are:

  • CPU: Dual core 1.6 GHz or higher
  • Memory: 2 GB or higher
  • Azure VM: A2 configuration or higher

Next steps

Learn more about Integrating your on-premises identities with Azure Active Directory.