# ExceptionFilter

**Kind:** Interface

**Source:** [`packages/common/interfaces/exceptions/exception-filter.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/common/interfaces/exceptions/exception-filter.interface.ts#L10)

**Part of:** [Common](subsystem-packages-common)

Interface describing implementation of an exception filter.

`ExceptionFilter` defines the contract for handling exceptions thrown during request processing. Implementations receive the thrown exception and an `ArgumentsHost`, allowing them to create framework-specific error responses, log failures, or transform errors before they reach the client.

## Diagram

```mermaid
graph LR
  A[Request Handler] -->|throws exception| B[ExceptionFilter.catch]
  B --> C[ArgumentsHost]
  C --> D[HTTP / RPC / WebSocket Context]
  B --> E[Formatted Error Response]
  E --> F[Client]
```

## Usage

```ts
import {
  ArgumentsHost,
  Catch,
  ExceptionFilter,
  HttpException,
} from '@nestjs/common';

@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter<HttpException> {
  catch(exception: HttpException, host: ArgumentsHost) {
    const response = host.switchToHttp().getResponse();
    const request = host.switchToHttp().getRequest();
    const status = exception.getStatus();

    response.status(status).json({
      statusCode: status,
      message: exception.message,
      path: request.url,
      timestamp: new Date().toISOString(),
    });
  }
}

// Register globally:
// app.useGlobalFilters(new HttpExceptionFilter());
```

## AI Coding Instructions

- Implement `catch(exception, host)` and use `host.switchToHttp()`, `switchToRpc()`, or `switchToWs()` for the active transport.
- Type the exception generic, such as `ExceptionFilter<HttpException>`, when the filter handles a specific error class.
- Add `@Catch(ErrorType)` to bind a filter to one or more exception types.
- Avoid exposing stack traces or internal error details in production responses.
- Register filters at the appropriate scope: method, controller, module provider, or globally with `useGlobalFilters()`.

## Used by

10 references from 10 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

### Imported by (10)

- `HttpExceptionFilter` — `integration/inspector/src/common/filters/http-exception.filter.ts`:8
- `RequestFilter` — `integration/websockets/src/request.filter.ts`:4
- `ApplicationConfig` — `packages/core/application-config.ts`:13
- `BaseExceptionFilterContext` — `packages/core/exceptions/base-exception-filter-context.ts`:11
- `BaseExceptionFilter` — `packages/core/exceptions/base-exception-filter.ts`:17
- `NestApplication` — `packages/core/nest-application.ts`:54
- `DependenciesScanner` — `packages/core/scanner.ts`:75
- `NestMicroservice` — `packages/microservices/nest-microservice.ts`:35

…and 2 more.