What is a thin client (lean client)?

Thin client use cases

Thin clients can be given to employees across industries for a number of reasons. They can be used to replace computers and to help access virtual desktops or virtualized applications. It is generally more cost-effective to use thin clients compared to a computer where all the processing is done locally. This is because each thin client doesn't need to be as new or powerful, considering most of the processing will be done server-side.

Thin clients could also be used in remote environments, so users don't have to worry about getting their PCs fixed as much. If the endpoint device is downloading most of its data from a server, there are fewer moving parts on the client side to worry about. In addition, organizations that need endpoint devices to be more secure may choose thin clients over other architectures.

Thin clients still may not be the best choice in every situation. For example, users would have to be in an environment where they have a strong and stable network connection. Intensive applications can run slow, as multiple people may be accessing the network at the same time. So thin clients are recommended more for organizations that make use of less intensive applications and have the back-end infrastructure to support the needs of each thin client.

Examples of thin clients in workplaces

An example of a thin client is a set of endpoint devices in a government office, where many people will use the same machine. Because the office data and applications are being accessed through a server and not locally, it is more secure. And because of the processing and computationally heavy tasks being done server-side, the endpoint device itself can be a bit older with less expensive hardware. Applications that may be hard for older computers to run can be pushed to the server, so performance still stays quick. Applications like Microsoft Windows Terminal Service could also be used as a proprietary protocol for remote desktops and applications

A library might also use a number of thin clients that connect to a central server in order facilitate the use of multiple devices at once that are all easily manageable.

Thin client architecture

Using a cloud computing-based architecture, a server in a data center will take on the processing load of multiple clients. Client hardware and software are kept rather lightweight, as the device only needs to make use of clients for essential applications. This also means the need for client-side setup or administration is reduced. User assets and data recovery tasks are also centralized for better visibility and scalability.

With the client side kept as lightweight as possible, the central server will take on much of the processing load. Because most of the data is being held in the central server, most of the focus in security is placed on securing the central server. Critical IT assets are also centralized in order to better use and allocate resources. Resources the central server will handle include memory and use of processor cores, for example.

How do thin clients work?

Thin clients can work within a shared terminal service, desktop virtualization or within a browser-based approach. In a shared terminal service, all clients share a server-based operating system and applications.

With desktop virtualization, each desktop is a virtual machine that is partitioned form a central server. This way of creating thin clients will have the central server partition resources to the appropriate clients. Even though the operating system and applications are not shared resources in this instance, they are still stored in the central server.

The browser-based approach is different from a normal thin client system in that the client will have functions execute from within a web browser, instead of on a central server. Data processing is done on the thin client. This form focuses on retrieving software and data that is held on a network.

Even though these approaches are different, in general, the goal is to keep client hardware and software as lightweight as possible. Client hardware will generally have low-energy processers, low levels of RAM, HDD space and will offer lower levels of performance compared to a normal computer. A minimum amount of processing power is needed to boot up the device and connect to the server. Thin clients are designed to be networked to a more powerful central server. Even though the client is not as powerful, users will still interact with it as if it were a normal computing device.

Thin client software should also be minimized. Software on the client side should be an operating system, and software that allows the device to connect the central server. Ideally, once the thin client is turned on, the device should receive the IP address and connect to a server using a protocol or another piece of software. The user can then log into the server and access the server's resources.

The central server each thin client connects to must be advanced enough to handle multiple client sessions at once and must be prepared to prevent outages and bottlenecks. The server should be able to connect to each client consistently in order to ensure each client can keep working.

Benefits of thin clients

The benefits of thin clients include:

• Less vulnerable to malware attacks
• Longer lifecycles
• Uses less power
• Less expensive to purchase than deploying regular PCs
• Better, centralized manageability
• More scalable

Drawbacks of thin clients

However, some downsides of thin clients include:

• Thin clients are extremely dependent on a continuous network connection.
• Networks are generally slower than relying on internal computer components.
• Bandwidth and performance can become a critical bottleneck.
• Servers must be sized correctly so they can deliver the right amount of resources to each client.

Thin clients vs. thick clients

Thin clients can be contrasted with thick clients, which are essentially desktop PCs that can handle all the functionality of a server if required. Thick clients have most resources installed locally, rather than distributed over a network. Thick client devices will use their own hard drives, software applications and other local resources. Most, if not, all essential components are contained in a thick client. 

A thin client, on the other hand, is a low-cost network computer that relies heavily on a server for its computational role. The idea of a thin client is to limit the computing capabilities to only essential applications. As opposed to thick clients, thin clients are more easily manageable, easier to protect from security risks and lower on maintenance and licensing costs.

The biggest difference between the two is that thin clients rely on a network connection for computing and don't do much processing on the hardware itself. Thick clients don't need the constant network connection and can do much of the processing for client/server applications.

A very thin client may be referred to as a zero client. A typical zero client product is a small box that connects a keyboard, mouse, monitor and Ethernet connection to a remote server. The server, which hosts the client's operating system and software applications, can be accessed wirelessly or with cable. Zero clients are often used in a virtual desktop infrastructure environment.

History of thin clients

Though thin clients might seem like a more modern invention, they have been around for quite some time; before even when the term was coined. Thin clients come from multi-user systems that would access a mainframe by a computer terminal. These would pivot from providing command-line interfaces to graphical user interfaces. In 1984, Unix would come to support devices that ran display server software, or graphical X terminals. In 1993, Tim Negris, vice president of server marketing at Oracle, coined the term "thin client." Negris hoped to differentiate their server-oriented software from Microsoft's desktop-oriented products. In 1995, Windows NT began supporting multi-user operating systems with Windows NT 3.51.

In the 2010s, thin clients started to broaden to not just PCs, but mobile devices like windows or Linux-based tablets.