CRT shaders are a popular category of shaders used in emulators to replicate the appearance of CRT displays. Modern CRT shaders are much more advanced than older attempts, offering sharp images and strong scanlines. The shaders can simulate different types of CRT displays, such as aperture grille CRTs and slot mask-style CRTs. It is best to use integer scaling with CRT shaders to avoid uneven lines and artifacts. RetroArch comes bundled with a variety of CRT shaders, including CRT-Geom, CRT-Caligari, CRT-Easymode, CRT-Hyllian, CRT-Lottes, GTU, ZFast_CRT, CRT-Royale, CRT-Guest-Advanced, and Sony Megatron. Each shader has its own unique features and settings.
https://emulation.gametechwiki.com/index.php/CRT_shaders