msmzd

When trying to add Optifine to a curseforge modpack, it crashes on startup. I've followed tutorials on how to do it and to my knowledge I've done everything right. I am using the correct optifine version for both the version of minecraft and forge. I download optifine from the official website, then drag and drop the jar file into the mods folder of the modpack. I start up the pack and get a crash every single time, regardless of the version of optifine or which modpack I try to install it on. Someone please tell me what I'm doing wrong.