If you have a beamer that has 4K support, that means it can accept content with a 4K resolution. 4K is a much sharper resolution than Full-HD, about four times as much (due to having 4 times the pixels). This is becoming the most popular resolution that's used by many modern streaming services, gaming consoles and TV channels.
However, a 4K resolution is not the same as 4K support. 4K support does not mean that the beamer has a native resolution of 4K. It simply means that your beamer downscales 4K content to its own resolution. That means it can still support 4K content without the beamer 'refusing' to project it (such as a black screen, cropped image or an error, for example). The projected image will not have the same detail as a native 4K beamer.
The most important thing to check is the native resolution of your beamer. The native resolution tells you what the projection quality will really be. Always make sure to double-check this specification, as some might say a true 720p beamer is a "4K beamer" because it supports 4K; that's not the case. 4K support simply tells you which video signals the beamer can receive and process.
For example, if you have a Full-HD beamer with 4K support, it will allow you to connect to modern 4K devices without problems. You're still able to enjoy a clear and sharp projection with a good brightness, contrast and focus. If you want the highest resolution and projection quality possible, then you're looking for a Native 4K Beamer. However, this is much more expensive and can cost a few hundred euro. And, if you watch Full HD content with a native 4K beamer, it doesn't transform that content to 4K.
For example, a Full HD beamer with 4K Support can be very useful. It allows you to connect modern 4K devices without compatibility problems. You can still enjoy a clear and sharp image, especially with good brightness, contrast, and focus. But if you want the highest possible detail, you should look for a beamer with native 4K resolution.
