Minecraft Forums

I'm sorry if this is overly simple or redundant, but I've never modded before and I'm a bit lost. I've been searching for a solution myself, but I'm thoroughly confused.

I only want to use the replay mod and their website states for the latest 1.11 build, I need Forge 1.11-13.19.0.2184. I've tried before and never got anywhere with it. I've yet to successfully install forge, much less any mods, and I'm determined to figure this out this time. As far as I'm aware, I've never installed a mod other than Optifine. Any help to point me in the right direction would be greatly appreciated.

---- Minecraft Crash Report ----

WARNING: coremods are present:
Contact their authors BEFORE contacting forge

// There are four lights!

Time: 12/19/16 11:35 PM
Description: Initializing game

java.lang.NoClassDefFoundError: bft
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.getField0(Unknown Source)
at java.lang.Class.getField(Unknown Source)
at net.minecraftforge.fml.client.FMLClientHandler.detectOptifine(FMLClientHandler.java:298)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:209)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:438)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:350)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: bft
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 15 more
Caused by: java.lang.NullPointerException
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
... 17 more

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Client thread
Stacktrace:
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.getField0(Unknown Source)
at java.lang.Class.getField(Unknown Source)
at net.minecraftforge.fml.client.FMLClientHandler.detectOptifine(FMLClientHandler.java:298)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:209)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:438)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:350)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.11
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_111, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 114069352 bytes (108 MB) / 292405248 bytes (278 MB) up to 3207856128 bytes (3059 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML:
Loaded coremods (and transformers):
Launched Version: 1.11-forge1.11-13.19.0.2184
LWJGL: 2.9.4
OpenGL: GeForce GTX 560 Ti/PCIe/SSE2 GL version 4.5.0 NVIDIA 375.95, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: Beautiful Skies, Lower Fire, Lower Shield, Mycelium Sides, Neutral End Rods, Transparent Pumpkin, Sticky Piston Sides, Wither Hearts, Clean Glass, Clean Stained Glass, Faithful Overdrive
Current Language: ~~ERROR~~ NullPointerException: null
Profiler Position: N/A (disabled)
CPU: 8x AMD FX(tm)-8120 Eight-Core Processor

If Optifine is the only mod that you are running is is best to install it by itself (double-click on the Optifine jar file and the installer should run, assuming that you have Java installed on your computer, not including the Java that Minecraft uses for itself) - Optifine does not require Forge, and has had a history of incompatibilities with Forge and/or other mods because of the way it modifies the game ("core mods" directly edit the game's code and are far more likely to have compatibility issues with Forge and other mods. Forge even has special code to detect if Optifine is installed since it is such a popular mod). The game also probably runs better with Optifine by itself because Forge adds a lot of stuff to the game so mods can use an API instead of directly modifying the game, which will slow it down. Also, since 1.11 only came out a short time ago Optifine and/or Forge are likely not fully debugged yet.

This most recent Optifine was already installed. I've had that for a while. I just changed the Optifine profile to use the Forge version that Forge installed into the launcher like the tutorial showed. Do I need to downgrade to a previous version of Optifine? How do I know which is compatible with Forge? Or can I not use Optifine and Forge at the same time right now?