Definition

zero client

Contributor(s): Ben Lutkevich

Zero client, also known as ultrathin client, is a server-based computing model in which the end user's computing device has no local storage. A zero client can be contrasted with a thin client, which retains the operating system and each device's specific configuration settings in flash memory. 

A typical zero client product is a small box that serves to connect a keyboard, mouse, monitor and Ethernet connection to a remote server. The server, which hosts the client's operating system (OS) and software applications, can be accessed wirelessly or with cable. Basically, they are bare-bones computers that rely on a server to handle many functions that a traditional PC, or thick client, would normally handle using its own hardware and software.

Zero clients are often used in a virtual desktop infrastructure (VDI) environment. This makes them ideal for remote work situations or distributed work environments.

How do zero clients work?

Zero clients are essentially input/output (I/O) redirection units. All user inputs (mouse clicks, keystrokes, etc.) are sent to a remote server, which returns data to display on a connected monitor. This is where the name "zero client" comes from -- almost all processing takes place on the server side, and almost zero processing takes place client-side.

Zero clients don't use an operating system and instead use firmware to connect to a remote device. An onboard processer is designed to use a sole protocol to communicate with a remote server -- usually PCoIP protocol to connect with the device. Firmware can be altered to support a different sole protocol, such as Microsoft RDP or Citrix HDX, but can only generally be optimized for one protocol at a time.

No data is stored on zero clients, because there is no local storage. Therefore all applications are provisioned and managed on a server in a remote data center, and served to the zero client device using its protocol.

Zero client hardware specifications

Zero clients are often physically small pieces of hardware -- meaning they have a small form factor. They are generally not more than a foot tall, around two inches wide, and weigh approximately two pounds. They typically include a processor with basic firmware installed on it, and some combination of ports including HDMI, DVI, DisplayPort, USB and Ethernet. There is also a port for a power supply.

Zero clients also tend to have line out and mic in ports, and usually also support wireless and VESA mounting. Some zero clients support multiple monitors.

How do zero clients differ from thin clients?

Both devices are used for the same purpose -- as high-performing endpoints that connect to a remote device and manage a centralized computing infrastructure.

Zero are clients are more lightweight, however. They have no operating system whereas a thin client has a minimal operating system.

Zero clients are only optimized for one connection type from one connection broker -- Microsoft, VMware and Citrix, for example -- and that broker's specific connection protocol. Thin client devices are optimized for multiple connection types.

Basically, zero clients do no client-side computing, and thin clients do minimal client-side computing. This makes zero clients more dependent on a network connection than thin clients.

zero client comparison diagram
A diagram comparing zero clients to thin and thick clients.

Benefits and drawbacks of zero client devices

The benefits of zero clients include:

  • Power usage can be as low as 1/50thof fat client requirements.
  • Devices are much less expensive than PCs or thin clients.
  • Efficient and secure means of delivering applications to end users.
  • No software at the client means that there is no vulnerability to malware.
  • Easy administration.
  • In a virtual desktop environment, administrators can reduce the number of physical PCs or blades and run multiple virtual PCs on server-class hardware.
  • Improved user experience stemming from increased hardware efficiency.

The drawbacks of zero clients include:

  • They often have limited ability to render graphics.
  • Performance depends on network connection because they rely on remote servers to do almost all processing.
  • Many zero clients are optimized for only one vendor or connection broker. Some may be reconfigured, but at best this is an inconvenience and at worst it leads to vendor lock-in.

Examples of zero clients

Vendors of zero client products include Digi International Inc., Teradici Corporation, Via Labs and Dell Wyse.

Some example zero client products include:

  • PD05 PCoIP zero client from EVGA
  • 10ZiG's 4448 series zero client
  • Dell Wyse 5030 Zero Client
  • MintWave MiNT-ACC ZERO
  • LG Box Type Zero Client CBV42-BP

Each product may differ slightly in its I/O features, what protocol connection it's optimized for and its price.

Zero clients are often used for VDI and allow users to efficiently virtualize their desktop remotely on laptops, tablets and mobile devices.

Zero clients and VDI

Zero clients are often used in VDI setups because of their unique benefits. They provide a traditional desktop experience without all the added maintenance, configuration and moving parts on the user's endpoint device.

Its lack of onboard storage and lack of OS provide little-to-no opportunity for hackers to access sensitive information or for the device to exposed to a virus. Zero clients also have relatively quick boot-up times, and require very little maintenance, which when necessary usually consists of simple firmware updates.

Additionally, zero clients can be remotely deployed and configured by IT administrators at scale because they are managed in a centralized computing infrastructure and do not require the IT worker to be in physical proximity with the device.

Users can load their virtual desktop on any endpoint, complete with personal preferences and configurations. This is convenient for times when an endpoint is experiencing a maintenance issue because the user can use a different device to access their remote desktop and have an identical desktop experience.

This was last updated in September 2020

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One of large market share leader in this space is "NComputing". refer www.ncomputing.com They have over 3M users in 100 countries especially K-12 US schools, India, Brazil...
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No mention of Sun Rays? I've been happily using these for over a decade (and the oldest ones still work with the newest server software), and post-Sun, Oracle are still making them...
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