Translations:Frequently asked questions/6/en
From Pixelmon Wiki
First, check the "Mods" section on Minecraft's main menu. If Pixelmon is not in the mods list, then a problem occurred during installation. If you are sure that you placed the downloaded Pixelmon jar file in the correct location (in the "mods" folder), check the file size of the Pixelmon jar. If it is significantly less than 300MB, then your download was corrupted. Try redownloading the Pixelmon jar.