Error map
ClassNotFoundException java.lang.ClassNotFoundException / NoClassDefFoundError
Java · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
Could not load file or assembly 'X, Version=…' or one of its dependencies
The runtime couldn’t find or load a referenced DLL — missing from the output, wrong version, or wrong platform (x86/x64).
java.lang.NullPointerException
Code called a method or accessed a field on a reference that is `null`.
Gradle: Could not resolve all files for configuration / Could not resolve dependency
Gradle couldn’t download a dependency — wrong coordinates/version, missing repository, offline mode, or network/proxy issues.
ModuleNotFoundError: No module named 'x'
Python can’t find the module you import — it isn’t installed in the interpreter/virtualenv that’s running, or the import path is…
Gradle: Unsupported class file major version / Android Gradle plugin requires Java 17 to run
The JDK running Gradle doesn’t match what the Gradle version or Android Gradle Plugin (AGP) supports.
Runtime.ImportModuleError: Unable to import module 'lambda_function': No module named 'x'
Lambda couldn’t load your handler file or one of its dependencies — the package is missing from the deployment zip/layer or the h…
error NU1101: Unable to find package X. No packages exist with this id in source(s): nuget.org
NuGet restore can’t find the package in any configured source — typo, private feed not configured/authenticated, or nuget.org mis…
Duplicate class X found in modules A and B
Two dependencies ship the same class — typically old Android Support libraries mixed with AndroidX, or Kotlin stdlib-jdk7/jdk8 ve…
error NU1605: Detected package downgrade: X from 8.0.1 to 8.0.0. Reference the package directly from the project to select a different version
A direct reference requests a lower version than a dependency needs, and NuGet treats the downgrade as an error.
[ERROR] Failed to execute goal on project x: Could not resolve dependencies for project
Maven couldn’t download or find one or more dependencies.
Error: Could not find or load main class org.gradle.wrapper.GradleWrapperMain
The Gradle wrapper JAR (gradle/wrapper/gradle-wrapper.jar) is missing or corrupt.
Your requirements could not be resolved to an installable set of packages.
Composer can’t find package versions that satisfy every constraint (PHP version, extensions, other packages).
Two steps away (32)
HTTP Error 500.30 - ASP.NET Core app failed to start
IIS/Azure’s ASP.NET Core Module launched your app but it crashed during startup.
Refused to execute script from 'x' because its MIME type ('text/html') is not executable
The browser fetched a script but the server labelled it text/html (usually an error page), so it refused to run it.
ChunkLoadError: Loading chunk 123 failed.
A lazily loaded JavaScript chunk couldn’t be downloaded — usually because a new deployment removed the old hashed files.
System.NullReferenceException: Object reference not set to an instance of an object
Code dereferenced a variable that is `null` — the .NET equivalent of Java’s NullPointerException.
TypeError: Cannot read properties of undefined (reading 'x')
You tried to access a property on a value that is `undefined` (or `null`) — usually data that hasn’t loaded yet or a wrong proper…
TypeError: 'NoneType' object is not subscriptable
You used `[ ]` on a value that is `None` — typically a function that returned nothing.
Android: INSTALL_FAILED_UPDATE_INCOMPATIBLE
An app with the same package name but a different signing key is already installed on the device.
Manifest merger failed: android:exported needs to be explicitly specified
Targeting Android 12 (API 31)+ requires `android:exported` on every activity, service or receiver that has an intent-filter.
CocoaPods could not find compatible versions for pod
pod install can’t satisfy the version constraints — outdated spec repo, a higher deployment target required, or two pods needing…
Error: Cannot find module 'x' (MODULE_NOT_FOUND)
Node can’t resolve the module path — the package isn’t installed, or a relative path/extension is wrong.
PHP Fatal error: Uncaught Error: Class "X" not found
PHP couldn’t load the class — autoloading failed, the namespace is wrong, or the dependency isn’t installed.
ImportError: cannot import name 'x' from 'y'
The module was found, but the name you’re importing from it doesn’t exist — usually a version change or a circular import.
java.lang.UnsupportedClassVersionError: class file version 61.0, this version of the Java Runtime only recognizes up to 55.0
Code compiled for a newer Java version is running on an older JVM.
ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
Build tools (Gradle, Maven, Android tools) can’t find a JDK.
[ERROR] Fatal error compiling: error: release version 17 not supported
The JDK running Maven is older than the Java version the project compiles for.
npm ERR! code ERESOLVE — unable to resolve dependency tree
npm 7+ found conflicting peer dependency requirements and refuses to install a broken tree.
npm ERR! code E404 — 404 Not Found: package@version is not in this registry
npm asked the registry for a package (or version) that doesn’t exist there — a typo, a private/scoped package without auth, or th…
java.lang.NoSuchMethodError
Code compiled against one version of a library is running with another version where the method doesn’t exist.
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './x' is not defined by "exports"
You imported a deep path inside a package that its package.json "exports" field doesn’t expose.
npm WARN EBADENGINE Unsupported engine / The engine "node" is incompatible with this module
A package requires a different Node.js version than the one you’re running.
DeprecationWarning: The `punycode` module is deprecated (DEP0040)
A dependency imports Node’s built-in punycode module, deprecated since Node 21.
ModuleNotFoundError: No module named 'distutils'
Python 3.12 removed distutils; old packages or tools that import it fail.
Unmet dependencies / E: Unable to correct problems, you have held broken packages
apt can’t find a set of package versions that satisfies all dependencies — usually mixed repositories or a package from another r…
0x8007007E: The specified module could not be found
A DLL that a program, driver or COM component needs isn’t on disk or on the DLL search path.
npm ERR! code ETARGET — No matching version found for package@^9.9.9
The version range in package.json doesn’t match any published version of the package.
npm WARN deprecated package@1.2.3: This package is no longer supported.
A dependency (often a transitive one) is deprecated by its author.
npm ERR! code EOVERRIDE — Override for x conflicts with direct dependency
An "overrides" entry sets a different version for a package you also depend on directly.
Dependency 'androidx.x:1.y' requires libraries and applications that depend on it to compile against version 34 or later of the Android APIs
A library needs a higher compileSdk than your module uses (checkAarMetadata task).
npm ERR! code ELIFECYCLE / Command failed with exit code 1
An npm script (build, start, test, postinstall) exited with an error. ELIFECYCLE is only the wrapper — the real error is printed…
COPY failed: file not found in build context / "/app/x": not found
The Dockerfile COPY refers to a path outside the build context, excluded by .dockerignore, or relative to the wrong directory.
Error: error:0308010C:digital envelope routines::unsupported
An old build tool (webpack 4, old react-scripts) uses a hash algorithm that OpenSSL 3 in Node 17+ disables.
Composer: PHP Fatal error: Allowed memory size of 1610612736 bytes exhausted
Composer ran out of memory while resolving or installing dependencies.
Map another error
Popular: 500403400ORA-009331064Critical errorFileNotFoundException assemblyTypeError