Skip to content
View in the app

A better way to browse. Learn more.
Forge Forums

A full-screen app on your home screen with push notifications, badges and more.

To install this app on iOS and iPadOS
  1. Tap the Share icon in Safari
  2. Scroll the menu and tap Add to Home Screen.
  3. Tap Add in the top-right corner.
To install this app on Android
  1. Tap the 3-dot menu (⋮) in the top-right corner of the browser.
  2. Tap Add to Home screen or Install app.
  3. Confirm by tapping Install.
Please read the rules and FAQ before starting a new topic
Currently supported: All versions

java.lang.NoClassDefFoundError : net/fabricmc/fabric/api/event/client/ClientTickCallback error every time I launch with a mod.

AinP
in Support & Bug Reports

Featured Replies

So basically every time I launch minecraft with a mod installed it crashes. If I take the mod out it launches fine.

 

I've had the same mod before and I'm pretty sure that the mod isn't what's causing the crash. When I first launch with fabric it loads fine and generates the mod folder and so on but as soon as I put a mod in the mod folder it crashes. 

I assume that It crashes because it is unable fo locate or find like a million classes, but again I really have no clue.

 

I've tried:

     Deleting the .minecraft folder and reinstalling.

     Deleting all versions and reinstalling.

     Updating Java.

     Reinstalling fabric and the mod (multiple times).

 

If someone understands this crashreport, here it is:

 

---- Minecraft Crash Report ----
// My bad.

Time: 2019-08-13 23:34
Description: Initializing game

java.lang.NoClassDefFoundError: net/fabricmc/fabric/api/event/client/ClientTickCallback
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at net.fabricmc.loader.util.DefaultLanguageAdapter.create(DefaultLanguageAdapter.java:45)
    at net.fabricmc.loader.EntrypointStorage$NewEntry.create(EntrypointStorage.java:101)
    at net.fabricmc.loader.EntrypointStorage$NewEntry.getOrCreate(EntrypointStorage.java:93)
    at net.fabricmc.loader.EntrypointStorage.getEntrypoints(EntrypointStorage.java:140)
    at net.fabricmc.loader.FabricLoader.getEntrypoints(FabricLoader.java:186)
    at net.fabricmc.loader.entrypoint.hooks.EntrypointClient.start(EntrypointClient.java:35)
    at net.minecraft.class_310.method_1503(class_310.java)
    at net.minecraft.class_310.method_1514(class_310.java:394)
    at net.minecraft.client.main.Main.main(Main.java:155)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:170)
    at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:129)
    at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:26)
Caused by: java.lang.ClassNotFoundException: net.fabricmc.fabric.api.event.client.ClientTickCallback
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:160)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 23 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.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at net.fabricmc.loader.util.DefaultLanguageAdapter.create(DefaultLanguageAdapter.java:45)
    at net.fabricmc.loader.EntrypointStorage$NewEntry.create(EntrypointStorage.java:101)
    at net.fabricmc.loader.EntrypointStorage$NewEntry.getOrCreate(EntrypointStorage.java:93)
    at net.fabricmc.loader.EntrypointStorage.getEntrypoints(EntrypointStorage.java:140)
    at net.fabricmc.loader.FabricLoader.getEntrypoints(FabricLoader.java:186)
    at net.fabricmc.loader.entrypoint.hooks.EntrypointClient.start(EntrypointClient.java:35)
    at net.minecraft.class_310.method_1503(class_310.java)

-- Initialization --
Details:
Stacktrace:
    at net.minecraft.class_310.method_1514(class_310.java:394)
    at net.minecraft.client.main.Main.main(Main.java:155)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:170)
    at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:129)
    at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:26)

-- System Details --
Details:
    Minecraft Version: 1.14.4
    Minecraft Version ID: 1.14.4
    Operating System: Windows 10 (amd64) version 10.0
    Java Version: 1.8.0_51, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 532503896 bytes (507 MB) / 1509949440 bytes (1440 MB) up to 2147483648 bytes (2048 MB)
    CPUs: 8
    JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
    Launched Version: fabric-loader-0.4.8+build.159-1.14.4
    LWJGL: 3.2.2 build 10
    OpenGL: NO CONTEXT
    GL Caps: 
    Using VBOs: Yes
    Is Modded: Definitely; Client brand changed to 'fabric'
    Type: Client (map_client.txt)
    Resource Packs: ~~ERROR~~ NullPointerException: null
    Current Language: ~~ERROR~~ NullPointerException: null
    CPU: <unknown>

This is the Forge forum, we don't provide Fabric support here.

This is my Forum Signature, I am currently attempting to transform it into a small guide for fixing easier issues using spoiler blocks to keep things tidy.

 

As the most common issue I feel I should put this outside the main bulk:

The only official source for Forge is https://files.minecraftforge.net, and the only site I trust for getting mods is CurseForge.

If you use any site other than these, please take a look at the StopModReposts project and install their browser extension, I would also advise running a virus scan.

 

For players asking for assistance with Forge please expand the spoiler below and read the appropriate section(s) in its/their entirety.

Spoiler

Logs (Most issues require logs to diagnose):

Spoiler

Please post logs using one of the following sites (Thank you Lumber Wizard for the list):

https://gist.github.com/: 100MB Requires member (Free)

https://pastebin.com/: 512KB as guest, 10MB as Pro ($$$)

https://hastebin.com/: 400KB

Do NOT use sites like Mediafire, Dropbox, OneDrive, Google Drive, or a site that has a countdown before offering downloads.

 

What to provide:

...for Crashes and Runtime issues:

Minecraft 1.14.4 and newer:

Post debug.log

Older versions:

Please update...

 

...for Installer Issues:

Post your installer log, found in the same place you ran the installer

This log will be called either installer.log or named the same as the installer but with .log on the end

Note for Windows users:

Windows hides file extensions by default so the installer may appear without the .jar extension then when the .log is added the log will appear with the .jar extension

 

Where to get it:

Mojang Launcher: When using the Mojang launcher debug.log is found in .minecraft\logs.

 

Curse/Overwolf: If you are using the Curse Launcher, their configurations break Forge's log settings, fortunately there is an easier workaround than I originally thought, this works even with Curse's installation of the Minecraft launcher as long as it is not launched THROUGH Twitch:

Spoiler
  1. Make sure you have the correct version of Forge installed (some packs are heavily dependent on one specific build of Forge)
  2. Make a launcher profile targeting this version of Forge.
  3. Set the launcher profile's GameDir property to the pack's instance folder (not the instances folder, the folder that has the pack's name on it).
  4. Now launch the pack through that profile and follow the "Mojang Launcher" instructions above.

Video:

Spoiler

 

 

 

or alternately, 

 

Fallback ("No logs are generated"):

If you don't see logs generated in the usual place, provide the launcher_log.txt from .minecraft

 

Server Not Starting:

Spoiler

If your server does not start or a command window appears and immediately goes away, run the jar manually and provide the output.

 

Reporting Illegal/Inappropriate Adfocus Ads:

Spoiler

Get a screenshot of the URL bar or copy/paste the whole URL into a thread on the General Discussion board with a description of the Ad.

Lex will need the Ad ID contained in that URL to report it to Adfocus' support team.

 

Posting your mod as a GitHub Repo:

Spoiler

When you have an issue with your mod the most helpful thing you can do when asking for help is to provide your code to those helping you. The most convenient way to do this is via GitHub or another source control hub.

When setting up a GitHub Repo it might seem easy to just upload everything, however this method has the potential for mistakes that could lead to trouble later on, it is recommended to use a Git client or to get comfortable with the Git command line. The following instructions will use the Git Command Line and as such they assume you already have it installed and that you have created a repository.

 

  1. Open a command prompt (CMD, Powershell, Terminal, etc).
  2. Navigate to the folder you extracted Forge’s MDK to (the one that had all the licenses in).
  3. Run the following commands:
    1. git init
    2. git remote add origin [Your Repository's URL]
      • In the case of GitHub it should look like: https://GitHub.com/[Your Username]/[Repo Name].git
    3. git fetch
    4. git checkout --track origin/master
    5. git stage *
    6. git commit -m "[Your commit message]"
    7. git push
  4. Navigate to GitHub and you should now see most of the files.
    • note that it is intentional that some are not synced with GitHub and this is done with the (hidden) .gitignore file that Forge’s MDK has provided (hence the strictness on which folder git init is run from)
  5. Now you can share your GitHub link with those who you are asking for help.

[Workaround line, please ignore]

 

Guest
This topic is now closed to further replies.
Go to topic listing

Important Information

By using this site, you agree to our Terms of Use.

I accept

Account

Navigation

Search

Search

Configure browser push notifications
Chrome (Android)
  1. Tap the lock icon next to the address bar.
  2. Tap Permissions → Notifications.
  3. Adjust your preference.
Chrome (Desktop)
  1. Click the padlock icon in the address bar.
  2. Select Site settings.
  3. Find Notifications and adjust your preference.