Ugdhar

Make your own thread, and be more descriptive what your problem is. Posting logs as described in the EAQ helps.

In your .minecraft (or if you changed the game directory, in there), there is a logs folder and it should contain debug.log

1.12 is no longer supported due to age. Please update to a modern version (1.14.4/1.15.2) to receive support. More information on supported versions can be found in the LTS link at the top of every page.

Please post the debug.log as described in the EAQ, preferably on some sort of pastebin hosting site. This should give more information so someone can give you a helping hand.

So Animefan already told you about the client-jar, and that you can go into .minecraft/versions to directly open the client jar. The minecraft wiki is also useful, as it breaks down the json formats and tells you what is available and what each element does. https://minecraft.gamepedia.com/Model Also make good use of google, and the search bar right on these forums. Try asking your question in different ways, class and method names are typically helpful when searching for stuff to help narrow it down. I think the main thing is to not get frustrated, nor to give up. And of course, once you really feel that you've looked and tried your best, you can always come and post on here, just make sure your explanation is complete, and you provide code and logs (github is your best friend for this), and people here are usually good at spotting things we miss.

Not sure if this is the issue, but I would not use special characters or spaces in path names, they can sometimes cause weird behavior with things. I would remove the spaces and the ! from this path (recreate the folders).

1.12 is no longer supported due to age. Please update to a modern (1.14.4+) version to receive support here. More information on supported versions can be found in the LTS link at the top of every page.

I have no idea, unless things were moved into a new folder or files were removed. Those would be the only 2 things I would thing would do that. Sorry.

what is the filename of your "first file" you pasted above? If it is called startserver.bat then you would type .\startserver.bat

Ok, so what you will probably want to do is open a command prompt or powershell window and run that "first file" from the commandline, and it will theoretically not just close on you so you can see what the actual error is saying. Hold shift and right-click in a blank spot in the folder that bat file is in, and you should get the option to open the powershell or command window there.

That code you pasted only sets some environment variables, it doesn't actually execute anything.

Nah, it creates it before you even click Single Player or anything.

I don't think the mods folder exists until you've started minecraft using that version of forge, you could always create it manually in the minecraft game folder

In your minecraft game directory mods folder. The default is the .minecraft folder in your home directory AppData\Roaming (on windows)

Make sure to read the changelog for Optifine, it tells you what versions of forge it works with. There is no forge compatible version of Optifine for 1.15.2 yet.

The one forge<version>mapped_snapshot should have all the vanilla/forge code in it. There's also a client-extra.jar containing client stuff like model jsons and such.

Please start your own thread, and post your debug.log as described in the EAQ

Please post the debug log as described in the EAQ

This thread is nearly 2 years old, if you're having an issue, you should make your own thread. Also please keep this forum in english. Keep in mind also that versions below 1.14.4 are no longer supported. See the LTS link at the top of every page.

Just no longer supported anymore. If you want to use it, there's no rule against it, but if you have problems, it is no longer supported. Read the LTS link at the top of every page, it gives more information on supported versions.

Please post logs as described in the EAQ, more info is needed Also please keep in mind versions below 1.14.4 are no longer supported due to age.

Really old versions are no longer supported. Please update to a modern (1.14.4 or 1.15.2) version to receive support. More information on supported versions can be found in the LTS link at the top of every page.

1.12 is no longer supported on these forums due to age. Please update to a modern version to receive support. More information on supported versions can be found in the LTS link at the top of every page.

1.12 is no longer supported on these forums due to age. Please update to a modern version to receive support. More information on supported versions can be found in the LTS link at the top of every page.

By downloading/installing/using a supported version of forge (and supported versions are listed in the LTS link. Read it, it's important). Long story short, 1.14.4 and 1.15.2 are supported, older versions are not. As far as I know you can still use it, but if you have problems, you will not get support on these forums.