If you are looking to get the best performance, here are some key takeaways from the community:
You might need to click "Preview Versions" on the official OptiFine download page to find the 1.19.1 release. Thanks for downloading Optifine 1.19.1
Simply download, run the JAR file with Java, and click "Install". Make sure your Minecraft launcher is closed first. If you are looking to get the best