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---
id: MutationCache
title: MutationCache
---
The `MutationCache` is the storage for mutations.
**Normally, you will not interact with the MutationCache directly and instead use the `QueryClient`.**
```tsx
import { MutationCache } from '@tanstack/react-query'
const mutationCache = new MutationCache({
onError: (error) => {
console.log(error)
},
onSuccess: (data) => {
console.log(data)
},
})
```
Its available methods are:
- [`getAll`](#mutationcachegetall)
- [`subscribe`](#mutationcachesubscribe)
- [`clear`](#mutationcacheclear)
**Options**
- `onError?: (error: unknown, variables: unknown, context: unknown, mutation: Mutation) => Promise<unknown> | unknown`
- Optional
- This function will be called if some mutation encounters an error.
- If you return a Promise from it, it will be awaited
- `onSuccess?: (data: unknown, variables: unknown, context: unknown, mutation: Mutation) => Promise<unknown> | unknown`
- Optional
- This function will be called if some mutation is successful.
- If you return a Promise from it, it will be awaited
- `onSettled?: (data: unknown | undefined, error: unknown | null, variables: unknown, context: unknown, mutation: Mutation) => Promise<unknown> | unknown`
- Optional
- This function will be called if some mutation is settled (either successful or errored).
- If you return a Promise from it, it will be awaited
- `onMutate?: (variables: unknown, mutation: Mutation) => Promise<unknown> | unknown`
- Optional
- This function will be called before some mutation executes.
- If you return a Promise from it, it will be awaited
## Global callbacks
The `onError`, `onSuccess`, `onSettled` and `onMutate` callbacks on the MutationCache can be used to handle these events on a global level. They are different to `defaultOptions` provided to the QueryClient because:
- `defaultOptions` can be overridden by each Mutation - the global callbacks will **always** be called.
- `onMutate` does not allow returning a context value.
## `mutationCache.getAll`
`getAll` returns all mutations within the cache.
> Note: This is not typically needed for most applications, but can come in handy when needing more information about a mutation in rare scenarios
```tsx
const mutations = mutationCache.getAll()
```
**Returns**
- `Mutation[]`
- Mutation instances from the cache
## `mutationCache.subscribe`
The `subscribe` method can be used to subscribe to the mutation cache as a whole and be informed of safe/known updates to the cache like mutation states changing or mutations being updated, added or removed.
```tsx
const callback = (event) => {
console.log(event.type, event.mutation)
}
const unsubscribe = mutationCache.subscribe(callback)
```
**Options**
- `callback: (mutation?: MutationCacheNotifyEvent) => void`
- This function will be called with the mutation cache any time it is updated.
**Returns**
- `unsubscribe: Function => void`
- This function will unsubscribe the callback from the mutation cache.
## `mutationCache.clear`
The `clear` method can be used to clear the cache entirely and start fresh.
```tsx
mutationCache.clear()
```
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