> For the complete documentation index, see [llms.txt](https://overmindjs.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://overmindjs.org/v27/api-1/addmutationlistener.md).

# addMutationListener

It is possible to listen to all mutations performed in Overmind. This allows you to create special effects based on mutations within a certain domain of your app, or whatever else you come up with. Note that this method triggers right after any mutation occurs, you might rather want to use **addFlushListener** to be notified about batched changes, like the components does.

{% tabs %}
{% tab title="overmind/onInitialize.ts" %}

```typescript
import { OnInitialize } from 'overmind'

const onInitialize: OnInitialize = async ({ state, localStorage }, overmind) => {
  overmind.addMutationListener((mutation) => {
    if (mutation.path.indexOf('todos') === 0) {
      localStorage.set('todos', state.todos)
    }
  })
}

export default onInitialize
```

{% endtab %}
{% endtabs %}


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