# Interceptors

> For the complete documentation index, see [llms.txt](https://docs.temporal.io/llms.txt).
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Interceptors wrap inbound and outbound Temporal calls so you can apply shared behavior such as tracing, logging, or
authorization. See [Interceptors](/encyclopedia/interceptors) for the inbound vs outbound model.

Register them on the Client (`client.Options.Interceptors`), the Worker (`worker.Options.Interceptors`), or both. Full
API: [`go.temporal.io/sdk/interceptor`](https://pkg.go.dev/go.temporal.io/sdk/interceptor).

## Implement a Client interceptor

Embed `ClientInterceptorBase` on a type that implements `InterceptClient`, and embed
`ClientOutboundInterceptorBase` on a type that overrides the calls you want to intercept. Forward every call you don't
override to `Next` so the rest of the chain still runs.

<!--SNIPSTART go-interceptor-client-->
[go-sandbox/workers/interceptors/interceptor.go](https://github.com/temporalio/documentation-sdk-code-examples/blob/main/go-sandbox/workers/interceptors/interceptor.go)
```go
type loggingClientInterceptor struct {
	interceptor.ClientInterceptorBase
}

func (loggingClientInterceptor) InterceptClient(
	next interceptor.ClientOutboundInterceptor,
) interceptor.ClientOutboundInterceptor {
	return &loggingClientOutboundInterceptor{
		ClientOutboundInterceptorBase: interceptor.ClientOutboundInterceptorBase{Next: next},
	}
}

type loggingClientOutboundInterceptor struct {
	interceptor.ClientOutboundInterceptorBase
}

func (l *loggingClientOutboundInterceptor) ExecuteWorkflow(
	ctx context.Context,
	in *interceptor.ClientExecuteWorkflowInput,
) (client.WorkflowRun, error) {
	log.Printf("starting workflow %q (%s)", in.Options.ID, in.WorkflowType)
	return l.Next.ExecuteWorkflow(ctx, in)
}
```
<!--SNIPEND-->

Register the interceptor when you create the Client:

<!--SNIPSTART go-interceptor-client-register-->
[go-sandbox/workers/interceptors/interceptor.go](https://github.com/temporalio/documentation-sdk-code-examples/blob/main/go-sandbox/workers/interceptors/interceptor.go)
```go
c, err := client.Dial(client.Options{
	Interceptors: []interceptor.ClientInterceptor{&loggingClientInterceptor{}},
})
```
<!--SNIPEND-->

Worker interceptors follow the same pattern for `WorkerInterceptorBase`, `WorkflowInboundInterceptorBase` /
`WorkflowOutboundInterceptorBase`, and `ActivityInboundInterceptorBase` / `ActivityOutboundInterceptorBase`. See the
[Logging Interceptor sample](https://github.com/temporalio/samples-go/tree/main/logger-interceptor) for a complete
Worker interceptor and its registration.

> **⚠️ Warning:**
> Workflow interceptors and replay
>
> Workflow interceptor methods also run during [replay](/develop/go/best-practices/testing-suite#replay). Use replay-safe
> APIs for logging, randomness, and time.
>

## Related

- [Observability - Tracing](/develop/go/platform/observability#tracing)
- [Context propagation](/develop/go/best-practices/context-propagation)
- [Logging Interceptor sample](https://github.com/temporalio/samples-go/tree/main/logger-interceptor)
- [Plugins - Interceptors](/develop/plugins-guide#interceptors)