angular-cn/aio/content/errors/NG0201.md

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@name No Provider Found @category runtime @videoUrl https://www.youtube.com/embed/lAlOryf1-WU @shortDescription No provider for {token} found!

@description You see this error when you try to inject a service but have not declared a corresponding provider. A provider is a mapping that supplies a value that you can inject into the constructor of a class in your application.

Read more on providers in our Dependency Injection guide.

@debugging Work backwards from the object where the error states that a provider is missing: No provider for ${this}!. This is commonly thrown in services, which require non-existing providers.

To fix the error ensure that your service is registered in the list of providers of an NgModule or has the @Injectable decorator with a providedIn property at top.

The most common solution is to add a provider in @Injectable using providedIn:

@Injectable({ providedIn: 'app' })