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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Angular NG0204 means Angular could not resolve a dependency while constructing a class. Start with the class and constructor parameter named in the error, then check its injectable metadata, whether the parameter has a runtime token, whether that token is provided in the consumer’s scope, and whether both sides use the same token instance.
What NG0204 means
Angular’s official error title is “Invalid Injection Token.” The error occurs when Angular cannot resolve a dependency for a class during dependency injection. Common causes include a class with dependencies that lacks @Injectable(), an unresolvable constructor parameter, or an InjectionToken without a suitable provider definition. See Angular’s NG0204 error reference.
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The wording helps narrow the problem. In Can't resolve all parameters for X: (?, ?, ?), each question mark indicates a constructor parameter Angular could not resolve. If the message says Token X is missing a ɵprov definition, the token lacks a provider definition; register a provider or give the token a suitable factory.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchHow to diagnose NG0204
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Identify the failing class and parameter
Read the full error and stack trace. Find the class Angular was constructing, then map each question mark in the “Can’t resolve all parameters” message to the constructor’s arguments in order. Begin with the marked parameter rather than changing unrelated providers.
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Check injectable metadata
If Angular is expected to construct a class that has constructor dependencies, ensure it has the appropriate
@Injectable()metadata. Angular’s error example demonstrates adding the decorator. Also check that the class being instantiated is the one with the metadata, rather than a similarly named class or an unintended import. -
Confirm the dependency has a runtime token
Angular needs a runtime value to identify a dependency. TypeScript interfaces and other type-only forms disappear after compilation, so they cannot serve as injection tokens. For interface-shaped configuration, functions, arrays, or parameterized types, define an
InjectionToken. Angular describes these cases in its InjectionToken API documentation. -
Check provider registration and scope
A valid token still needs a provider available to the consumer, unless it has a suitable factory or is otherwise automatically provided. Angular supports automatic provision through
@Injectablemetadata or a token factory, as well as manual provider arrays. See the dependency provider guide.Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy.Choose a provider strategy based on what the dependency represents:
useClassconstructs an implementation,useValuesupplies a fixed value,useFactorycreates a value, anduseExistingaliases another provider. Confirm the registration is in a scope visible to the code requesting the dependency. -
Verify token identity
An
InjectionTokendescription is for debugging; Angular identifies the token by its object reference. The provider and consumer must use the same exported token instance. Creating two tokens with identical descriptions does not make them interchangeable. Define the token once in a shared module or file, then import that token at both the provider and injection sites. Angular documents token identity in the InjectionToken API and DI debugging guide.
A safe pattern for interface-shaped dependencies
Use one shared token for the interface-shaped value, provide it, and inject that same token. The generic type helps TypeScript check usage; the token object supplies the runtime identity Angular needs.
import { InjectionToken, inject } from '@angular/core';
export interface AppConfig {
apiBaseUrl: string;
}
export const APP_CONFIG = new InjectionToken<AppConfig>('app.config');
// In an appropriate provider scope:
{ provide: APP_CONFIG, useValue: { apiBaseUrl: '/api' } }
// In a class or another supported injection context:
const config = inject(APP_CONFIG);Adapt the provider strategy and scope to the application. A token factory is another option when the value can be created by the token’s factory configuration; it is not a substitute for using the same token object at both ends.
Why common quick fixes may not work
- Adding
@Optional()does not create a runtime token. It can make a valid dependency optional when no provider is found, but it cannot turn an interface into a runtime token or make two distinctInjectionTokenobjects identical. - Matching token descriptions is not enough. Re-create neither the provider token nor the injection token independently; import the one shared instance.
- Adding a provider in the wrong scope may not help. The provider must be visible to the consumer requesting the dependency.
Make sure the error is really NG0204
Nearby Angular DI errors point to different failure layers, so use the code actually reported before changing provider setup.
Quick Recap
| Error | What it indicates | Where to look |
|---|---|---|
| NG0204 | Angular cannot resolve a dependency for a class. | Class metadata, constructor token, provider registration and scope, or token identity. Angular error reference. |
| NG0203 | inject() was called outside an injection context. |
Move the call to a supported context, such as construction, field initialization, or a provider or token factory. A later lifecycle hook is outside the supported context. Angular error reference and inject API documentation. |
| NG2003 | Angular has no runtime token for a constructor parameter, often because the parameter uses a primitive type. | Provide a runtime token, commonly an InjectionToken, and configure its provider as needed. Angular error reference. |
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