How to use a laptop as ONLY monitor [duplicate]

Is it possible to make my laptop's screen act as a second monitor for my desktop computer?

Here's an interesting freeware solution:

ZoneScreen

To my knowledge, spacedesk is the best:

• No issues with unsigned drivers
• No issues with aero
• Free, at least current beta
• Supports either windows app, or any html-5 web browser as "client"
• Windows 10 / 8.1 / 8 / 7 (x86 and x64)

Cons: This tool (probably, just like all other today's tools) is unable to provide nice FPS together with high image resolution and color depth. Even if link speed itself is not the issue (e.g. if you have 1Gbps LAN connection) "motion smoothness" is still far from perfect. So, although this solution is suitable for tasks like office work, it is hardly suitable for video/gaming.

Maxivista is a commercial software that lets you do this.

The following product is advertised as compatible with Windows 8 :

Air Display

Air Display is an app that lets you connect an iPad, Android tablet, or Mac or Windows computer as a secondary display to a primary Mac or PC desktop using your wireless network. By default Air Display is set to function in Extended Desktop mode.

Though perhaps not exactly what you want, you could use synergy between computers (OS independent too!). As well, you can copy both text and files across the computers, so for all intents and purposes they act as one computer (though still use their own hardware).