Since 1.9 lag is unbearable, I decided to go back to the version of Minecraft that I first started playing which is 1.3.1. I've been wanting to install Optifine so I can run my texture pack without using MCPatcher. I tried going to the 1.3.1 jar that is located in the versions older in the .minecraft folder and installing it the old way; dragging the files from Optifine on to the 1.3.1 jar and deleting the META-INF folder. I did this, relaunched Minecraft and Optifine is still not installed.
I'm not really a computer genius and this probably has an easy fix but what exactly am I doing wrong? Is it possible to install mods on older versions with this new launcher?
In order to install mods with the current launcher the steps are much more complicated; first, you have to copy the folder for the version you want to mod (1.3.1). Next, rename the folder and the jar and json files inside; for example, to "1.3.1_mods"; then use a text editor to open the json file and near the beginning is a line that reads "id": "1.3.1" - change that to the same name you used for the files and folder ("id": "1.3.1_mods"). After that, you need to go near the end of the json file and you should see see a section that starts with "downloads" and includes a download link for the jar (named "client.jar" with a long series of letters and numbers before it). You'll want to delete that entire section so the launcher doesn't know where to redownload the jar as otherwise it will replace it even if you renamed it (before a few months ago just renaming it was sufficient). See this example for 1.8.8; the 1.3.1 json has the same format. Afterwards the steps to install the mod itself are the same; the modified version should now show up in the profile editor as "1.3.1_mods" or whatever you named it (if it doesn't you need to restart the launcher or the json file wasn't edited correctly) and the "Play" button should not say anything like "Ready to update and play".
Actually, I happen to have the "original" json file (without the downloads stuff) for 1.3.1 on my computer since I downloaded it a year ago and never played it since so the json wasn't updated; I don't know if you can distribute it though (it is forbidden to distribute jars themselves) as I could give it to you; you would just have to rename it and change the "id" inside (the launcher doesn't try to update a renamed json file).
Also, there is another way to install mods that doesn't require directly modifying the jar; instead you add the mod as a library so it is loaded at runtime. The steps are more involved and can be found here; I have not tried this recently but it worked for me back in 1.6.2 when I did this to install Optifine and some of my own non-Forge mods into Forge, and as mentioned above the launcher doesn't redownload modified jsons:
Ignore the stuff mentioning Forge unless you have it. If it isn't already a jar file (I believe only newer versions with an installer come in jar files, older versions are zip), change the extension of the Optifine file to jar so it is a "jar file" (trying to run it will give you an "invalid or corrupt jar file" error but it appears to load fine). While probably not relevant for you this method also makes it easier to update mods; simply edit the json to remove or change them instead of making a whole new jar each time.
Since 1.9 lag is unbearable, I decided to go back to the version of Minecraft that I first started playing which is 1.3.1. I've been wanting to install Optifine so I can run my texture pack without using MCPatcher. I tried going to the 1.3.1 jar that is located in the versions older in the .minecraft folder and installing it the old way; dragging the files from Optifine on to the 1.3.1 jar and deleting the META-INF folder. I did this, relaunched Minecraft and Optifine is still not installed.
I'm not really a computer genius and this probably has an easy fix but what exactly am I doing wrong? Is it possible to install mods on older versions with this new launcher?
In order to install mods with the current launcher the steps are much more complicated; first, you have to copy the folder for the version you want to mod (1.3.1). Next, rename the folder and the jar and json files inside; for example, to "1.3.1_mods"; then use a text editor to open the json file and near the beginning is a line that reads "id": "1.3.1" - change that to the same name you used for the files and folder ("id": "1.3.1_mods"). After that, you need to go near the end of the json file and you should see see a section that starts with "downloads" and includes a download link for the jar (named "client.jar" with a long series of letters and numbers before it). You'll want to delete that entire section so the launcher doesn't know where to redownload the jar as otherwise it will replace it even if you renamed it (before a few months ago just renaming it was sufficient). See this example for 1.8.8; the 1.3.1 json has the same format. Afterwards the steps to install the mod itself are the same; the modified version should now show up in the profile editor as "1.3.1_mods" or whatever you named it (if it doesn't you need to restart the launcher or the json file wasn't edited correctly) and the "Play" button should not say anything like "Ready to update and play".
Actually, I happen to have the "original" json file (without the downloads stuff) for 1.3.1 on my computer since I downloaded it a year ago and never played it since so the json wasn't updated; I don't know if you can distribute it though (it is forbidden to distribute jars themselves) as I could give it to you; you would just have to rename it and change the "id" inside (the launcher doesn't try to update a renamed json file).
Also, there is another way to install mods that doesn't require directly modifying the jar; instead you add the mod as a library so it is loaded at runtime. The steps are more involved and can be found here; I have not tried this recently but it worked for me back in 1.6.2 when I did this to install Optifine and some of my own non-Forge mods into Forge, and as mentioned above the launcher doesn't redownload modified jsons:
http://minecraft.gamepedia.com/Mods/Installing_OptiForge/Forge_Installer#Download_OptiFine
Ignore the stuff mentioning Forge unless you have it. If it isn't already a jar file (I believe only newer versions with an installer come in jar files, older versions are zip), change the extension of the Optifine file to jar so it is a "jar file" (trying to run it will give you an "invalid or corrupt jar file" error but it appears to load fine). While probably not relevant for you this method also makes it easier to update mods; simply edit the json to remove or change them instead of making a whole new jar each time.
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?