Enable Borderless Windowed Mode
Accessing the Settings
Open Minecraft and launch the game. Once in-game, access your settings menu. Look for video or graphics options—the exact location depends on your launcher version, but it's typically under Options > Video Settings.
Activating Windowed Fullscreen
Within the video settings, locate the fullscreen toggle or mode selector. You should see an option for Fullscreen Mode or similar. Change this from "Fullscreen" to "Windowed Fullscreen" or enable the borderless windowed option if presented as a checkbox.
Apply the changes and the game will restart into borderless windowed mode. Your game window will now fill your screen without borders, but you'll retain the ability to alt-tab and see your taskbar.
Confirming the Mode
You'll know it's working when Minecraft appears to fill your entire monitor but you can still access other windows by moving your cursor to screen edges or using keyboard shortcuts. The window won't have the typical title bar or resize handles visible.