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Angular’s NG0201 means dependency injection could not find a provider for a token the code requested. Start with the token named in No provider for …, then check that the exact runtime token is registered in an injector the requesting code can reach. The dependency path in the error helps identify where the failed lookup occurred.
What NG0201 means—and where to start
NG0201 is Angular’s No Provider Found error. A class, component, or other injectable requested a dependency, but Angular could not resolve a provider for that token. The error may include a path such as App -> AuthClient -> UserClient. In that example, UserClient is the unresolved dependency; trace the path backward to see which consumer ultimately requested it. Angular’s NG0201 reference recommends working backward from the missing provider named by the error.
Keep NG0201 distinct from related dependency-injection errors: NG0203 concerns calling inject() outside an injection context, while NG0200 indicates a circular dependency. Angular lists these separately in its Error Encyclopedia.
Follow this diagnostic sequence
- Read the complete error. Note the error code, the missing token, and any dependency path. Begin with the final unresolved token in that path.
- Verify the token and import. Check that the consumer injects the intended class or
InjectionToken, and that the provider registers the same runtime token object. Similar names do not make two token objects interchangeable. - Check how the provider is registered. For a service class, confirm it has the Angular injectable metadata required by the project’s version, and that it is provided either through suitable
@Injectablemetadata or a reachableprovidersarray. - Check injector visibility. Angular searches the relevant injector hierarchy from the requester upward; it does not search down into a child injector. A provider on a child component therefore cannot satisfy a parent or sibling that requests the service.
- Check framework setup and version. For framework services such as
HttpClient, use the setup guidance for the Angular major version and bootstrap style in the project. - Inspect the injector tree if registration appears correct. Angular DevTools can show providers by injector. Determine whether the token is missing or registered only in a scope the failing requester cannot reach.
Angular’s dependency-injection troubleshooting guide covers dependency paths, common scope mistakes, and injector inspection.
#1 Best Overall
Choose a provider location that matches its consumers
There is no single correct place to register every service. Choose scope based on who needs the token and whether those consumers should share an instance. Angular supports automatic service provision and manual providers in application configuration, NgModules, routes, components, and directives; see Defining dependency providers.
| Provider approach | Reach and typical use | Instance consideration |
|---|---|---|
@Injectable({ providedIn: 'root' }) |
Application-wide availability for a class service when broad access is intended. | Suitable when consumers should use the application-level service rather than a separately scoped local instance. |
| Application or NgModule provider | Register a service or value at the application or module configuration level when its consumers belong there. | Scope depends on the injector configuration and application structure. |
| Route provider | Available in the route’s child injector and its route context. | Useful when the dependency belongs to a route subtree rather than the entire application. |
| Component or directive provider | Available within that component or directive’s injector subtree. | A local provider can give that subtree a scoped instance, separate from providers elsewhere. |
InjectionToken provider |
Use for configuration, primitives, functions, or values described by a TypeScript interface. | Register the exact token with a value, factory, or other provider at the scope its consumers can reach. |
Angular’s hierarchical injector guide explains how lookup works across injector levels. Move a provider upward only as far as the intended consumers require: broadening its scope changes who can resolve it and can affect instance sharing.
Use InjectionToken for interface-shaped values
TypeScript interfaces are erased at runtime, so an interface alone cannot serve as an injection token. Define an InjectionToken<T> and register a provider for that token instead. For example:
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export interface AppConfig {
apiBaseUrl: string;
}
export const APP_CONFIG = new InjectionToken<AppConfig>('app.config');
// In an appropriate providers array:
{ provide: APP_CONFIG, useValue: { apiBaseUrl: '/api' } }Inject APP_CONFIG wherever the configuration is needed, rather than attempting to inject AppConfig. The token and its provider must refer to the same token object.
Rank #3
Check HttpClient setup against the Angular version
Do not assume every Angular release configures HttpClient the same way. Angular’s current HttpClient setup guide says it is available for injection by default in Angular v21 and later. The guide also documents provideHttpClient() for application providers and for NgModule providers in NgModule-based bootstrap. For earlier versions, follow the setup instructions for that specific release and bootstrap style rather than applying the v21-and-later default.
Use optional injection only when absence is expected
Angular’s inject API supports optional injection; if the token is not found, the result is null. This is appropriate only when the dependency is genuinely optional and the code handles the null case. Making a required dependency optional does not register its provider—it replaces a clear missing-provider failure with a nullable result.
Use version-appropriate decorator guidance
For class services, use the @Injectable API and provider configuration documented for the Angular version in the project. Angular’s versioned v18 NG0201 page and stable Inject API documentation use @Injectable for service metadata. Do not copy a different decorator label from a rendered error-page snippet without confirming it against the installed version’s API documentation.
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