Prepare to install OptiFine
Download OptiFine. To install the OptiFine mod on a Windows or Mac computer, you need to download the JAR OptiFine file:
Access https://wminecraft.net/optiforge-mod/ in a web browser on your computer.
Click Download to the right of the OptiFine link at the top, below the “OptiFine HD Ultra” heading.
Wait 5 seconds, then click SKIP AD in the upper-right corner of the screen (you may need to click Continue on the ad blocking warning first).
Click the Download OptiFine link in the middle of the page.
Click Keep or Allow if the browser warns you that OptiFine might be dangerous.
You can skip this step if you want to run OptiFine as a native Minecraft configuration, which is supposed to be easier than installing Forge if your computer doesn’t already have one.