Client Access License

Definition of Client Access License

A Client Access License (CAL) is a type of software license that grants multiple end users the legal permission to access and use server-based resources, like operating systems or applications, on a network. CALs are generally required by the software’s vendor, such as Microsoft, for each user or device in a network that will be connecting to their server product. This licensing model ensures that organizations pay for the appropriate level of access to the server resources while optimizing resource allocation and performance.


The phonetic pronunciation of the keyword “Client Access License” is as follows:- Client: ˈklaɪənt- Access: ˈækses- License: ˈlaɪsəns

Key Takeaways

  1. Client Access Licenses (CALs) are required for users or devices to access resources on a Windows Server.
  2. CALs come in two types: User CALs and Device CALs, allowing organizations to choose the licensing model that best suits their needs.
  3. Microsoft offers different CAL editions corresponding to Windows Server editions, ensuring that businesses can efficiently scale their licensing according to their requirements.

Importance of Client Access License

The technology term “Client Access License” (CAL) is important because it refers to the legal permission that allows client devices or users to access and utilize the services and features provided by server software, such as databases, messaging systems, and other resources.

CALs play a crucial role in managing and regulating the usage of server-based applications, ensuring compliance with software vendor licensing requirements, and controlling access to proprietary technology.

They help establish a fair pricing model for organizations by allowing them to pay only for the number of users or devices accessing the server, rather than purchasing multiple standalone software licenses.

Ultimately, Client Access Licenses help maintain the integrity and security of server resources while promoting efficient and cost-effective utilization of server-based applications in a digital environment.


The purpose of Client Access License (CAL) is to provide a legal and streamlined manner for end-users to access and utilize the features of certain server-based software products. CALs serve as a means to manage and measure the utilization of these products within an organization, ensuring that organizations pay for the amount of users or devices that actively use the software.

This enables businesses to scale their software usage alongside their own growth, and allows them to comply with the licensing regulations set forth by software vendors without having to purchase a license for every device accessing the software. This licensing model is commonly used by companies providing server-based applications such as Microsoft, where software products like Windows Server, SQL Server and Exchange Server require CALs to be purchased.

There are basically two types of CALs: User-based CALs and Device-based CALs. User-based CALs permit individual users to access the server software from multiple devices, whereas Device-based CALs allow multiple users to access the server software but only from a single, designated device.

By employing CALs in server software management, businesses have the flexibility to choose the best licensing approach for their specific needs. This custom approach can lead to cost savings and better control over resource allocations within their network infrastructure and simultaneous compliance with software licensing requirements.

Examples of Client Access License

A Client Access License (CAL) refers to the licensing model used by various software vendors, including Microsoft, where access and usage rights are granted to users and devices. In this model, both the server software and its connected clients require licenses. Here are three real-world examples where Client Access Licenses (CALs) are applicable:

Microsoft Windows Server: In a medium-sized organization, while managing the company’s computer systems, the IT department may choose to deploy a Windows Server, such as Windows Server 2019, to control the network, file storage, and manage other company-wide services. To allow users and devices to legally use the Windows Server infrastructure, the company would need to purchase CALs for each employee, device, or concurrent connection that requires access to that server.

Microsoft SharePoint: A corporation may use Microsoft SharePoint as an intranet platform for collaboration, file storage, and detailed communication among employees and third-party partners. To enable team members to access SharePoint features and benefit from its collaborative tools, the organization must have a CAL for each user or device that needs access to the SharePoint server.

Microsoft SQL Server: A software development company might create a custom application utilizing SQL Server as its backend database. All users and devices that require access to this SQL database will need a CAL or a Core-based licensing option, depending on the licensing model chosen by the company. This provides a legal and cost-effective way of ensuring the company remains compliant with the software vendor’s licensing agreements.

Client Access License FAQ

What is a Client Access License (CAL)?

A Client Access License (CAL) is a type of license that allows clients to connect to certain server software and access their features, functionalities, and resources. CALs are typically required for Microsoft server products, such as Windows Server, SQL Server, and Exchange Server.

Why do I need a Client Access License?

A Client Access License is needed to ensure that your organization is compliant with the licensing requirements for software products like Microsoft Windows Server. It grants access to specific server resources, enabling your users to connect and utilize their features legally.

What types of CALs are available?

There are two main types of CALs: User CALs and Device CALs. User CALs grant access to the server for individual users, while Device CALs grant access for specific devices. The choice between User and Device CALs depends on your organization’s needs and the way your users interact with the server.

How do I know how many CALs I need?

To determine the number of CALs you need, you must consider the number of users or devices that will be accessing the server. For User CALs, count the total number of users who will need access. For Device CALs, count the total number of devices that will connect to the server. You must have enough CALs to cover either the total users or devices, depending on the CAL type you choose.

Can I mix User CALs and Device CALs?

Yes, you can mix User CALs and Device CALs, depending on the needs of your organization. For example, you may choose User CALs for employees who need access from multiple devices and Device CALs for devices shared among multiple employees, such as company-issued computers, ensuring that your organization remains compliant with licensing requirements.

Related Technology Terms

  • License Management
  • Server Client Relationship
  • Network Authentication
  • User and Device Access
  • Software Licensing Compliance

Sources for More Information

  • Microsoft Documentation –
  • Techopedia –
  • TechRepublic –
  • Search Windows Server –

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