How to get CSGO 4:3 resolution with black bars or stretched on XL monitors?

The display aspect ratio and use of black bars is up to individual preference. There isn't one optimal way for all. Some pro players prefer stretching, black bars, or full screen. 

The following chart lists all configuration parameters for different display settings.

If you are using Nvidia graphics card and prefer to adjust by display, open the control panel > to perform scaling on "Display" > select "full-screen" mode

• to get a 4:3 image with black bars,  go to display menu > select display mode > choose  "Aspect"
• to get stretched image without black bars, go to display menu > select display mode > choose  "Full"
  
  

If you are using Nvidia graphics card and prefer to adjust by GPU, open the control panel > to perform scaling on "GPU"

• to get a 4:3 image with black bars,  select the scaling mode of  "Aspect ratio"
• to get a stretched image without black bars, select the scaling mode of "Full-screen"

If you are using AMD graphics card and prefer to adjust by display, open the control panel > go to “GPU Scaling > turn off “Enable” button

• to get a 4:3 image with black bars,  go to display menu > select display mode > choose  "Aspect"
• to get stretched image without black bars, go to display menu > select display mode > choose  "Full"

If you are using AMD graphics card and prefer to adjust by GPU, open the control panel > go to “GPU Scaling” > turn on “Enable” button

• to get a 4:3 image with black bars, select “Preserve aspect ratio”  
• to get a stretched image without black bars, select “Full panel”

To learn more about XL Monitors