Error map
500.30 HTTP Error 500.30 - ASP.NET Core app failed to start
.NET · 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)
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
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).
[nodemon] app crashed - waiting for file changes before starting...
Your app threw an error on startup; nodemon is waiting for a file change to retry.
java.lang.ExceptionInInitializerError
A static initializer (static block or static field) threw an exception while the class was loading.
InvalidOperationException: Unable to resolve service for type 'X' while attempting to activate 'Y'
ASP.NET Core’s dependency injection container can’t build Y because one of its constructor dependencies (X) was never registered.
Job for mysql.service failed because the control process exited with error code
The MySQL/MariaDB service failed to start — the real reason is in the MySQL error log.
FATAL: the database system is starting up
PostgreSQL is still starting (or recovering) and not accepting connections yet.
FATAL: lock file "postmaster.pid" already exists — Is another postmaster running in data directory?
PostgreSQL won’t start because a stale postmaster.pid file remains (or another instance really is running).
Pod status Init:CrashLoopBackOff / Init:Error
An init container keeps failing, so the pod’s main containers never start.
HTTP Error 500.19 - Internal Server Error: The requested page cannot be accessed because the related configuration data for the page is invalid
IIS can’t read web.config — usually the ASP.NET Core Hosting Bundle (AspNetCoreModuleV2) or URL Rewrite module isn’t installed, o…
The framework 'Microsoft.NETCore.App', version '8.0.0' (x64) was not found. You must install or update .NET to run this application
The machine doesn’t have the .NET runtime version the app was built for (framework-dependent deployment).
Docker container keeps restarting (Restarting (1) x seconds ago)
The container crashes on start and its restart policy (always/unless-stopped/on-failure) starts it again in a loop.
Two steps away (29)
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 502 Bad Gateway
A proxy or gateway (Nginx, load balancer, CDN) got an invalid response — or no response — from the upstream server behind it.
HTTP 503 Service Unavailable
The server is temporarily unable to handle the request — overloaded, in maintenance, or has no healthy backends.
java.lang.ClassNotFoundException / NoClassDefFoundError
The JVM couldn’t find a class on the classpath at runtime.
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.
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.
Error: listen EADDRINUSE: address already in use :::3000
Another process is already listening on that port.
npm ERR! could not determine executable to run
npx couldn’t find a binary to run for that package.
LOG: could not bind IPv4 address "0.0.0.0": Address already in use — Is another postmaster already running on port 5432?
Another process (often a second PostgreSQL install or a container) already listens on 5432.
Docker container exits immediately (Exited (0) / Exited (1) right after start)
The container started and its main process finished at once, so the container stopped — Docker containers only live as long as PI…
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.
JsonException: A possible object cycle was detected
System.Text.Json found a reference loop (e.g. Order → Customer → Orders → …) while serialising, usually from EF Core navigation p…
UnsatisfiedDependencyException / NoSuchBeanDefinitionException: No qualifying bean of type 'X' available
Spring couldn’t find (or choose) a bean to inject.
MySQL ERROR 2002 (HY000): Can't connect to local MySQL server through socket
The client couldn’t reach the MySQL server — it isn’t running, or the client is looking for the socket/port in the wrong place.
FATAL: data directory "/var/lib/postgresql/data" has invalid permissions — Permissions should be u=rwx (0700) or u=rwx,g=rx (0750).
PostgreSQL refuses to start because the data directory is too open or owned by the wrong user.
FATAL: database files are incompatible with server — The data directory was initialized by PostgreSQL version 15, which is not compatible with this version 16
A newer (or older) PostgreSQL major version was started on an existing data directory.
Kubernetes: CrashLoopBackOff
The container starts, crashes (or exits), and Kubernetes keeps restarting it with increasing back-off delays.
Kubernetes: CreateContainerConfigError — secret / configmap not found
Kubernetes can’t build the container’s configuration — usually a referenced Secret, ConfigMap or key doesn’t exist in that namesp…
Pod status InvalidImageName: couldn't parse image reference
The image field in the pod spec isn’t a valid image reference, so the kubelet can’t even try to pull it.
Windows Error 0x80070005 (E_ACCESSDENIED): Access is denied
Windows refused an operation because the account or process lacks permission — seen in Windows Update, installers, Task Scheduler…
ObjectDisposedException: Cannot access a disposed context instance
Code used a DbContext after its scope ended — usually async void, fire-and-forget tasks, or capturing a scoped context in a singl…
InvalidOperationException: Collection was modified; enumeration operation may not execute
A list/dictionary was changed while a foreach loop was iterating it.
Azure App Service: ":( Application Error" / container didn’t respond to HTTP pings
App Service started your app but it crashed or never listened on the expected port.
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.
SyntaxError: Unexpected token '<' (HTML served instead of JavaScript)
The browser loaded a .js file but received HTML (an error page or the SPA index.html).
Kubernetes: OOMKilled (exit code 137)
The container used more memory than its limit, and the kernel killed it.
Conflict. The container name "/x" is already in use by container …
A container (running or stopped) already has that name; Docker won’t create a second one with the same name.
Error response from daemon: Container X is not running
You tried to exec into or interact with a container that has stopped.
Map another error
Popular: 4035004000xC000007BTypeErrorCritical error404NullPointerException