Understanding what it's all about
This mod works exclusively with Fabric - Minecraft without Forge versions.
Attention: Development of this mod version has been discontinued.
For macOS users experiencing full-resolution rendering issues on retina displays since version 1.13, the retiNO mod may help.
For other cases, there's an enhanced version of this project called ResolutionControl+, which UltimateBoomer has continued.
Resolution Control provides the ability to render Minecraft's 3D portion (the game world) at a lower resolution followed by upscaling using the nearest-neighbor method. A comprehensive settings screen (default key P) allows for dynamic parameter adjustments during gameplay.

Why this was created
The mod initially emerged as a solution to full-resolution rendering problems on retina monitors after Minecraft 1.13's release, which significantly reduced performance on my computer. Alternative resolution reduction methods used linear scaling, creating blurry and unpleasant visuals compared to the previously used nearest-neighbor method. Resolution Control became exactly the solution to this problem!