# createUseFetch
> A factory function to create a custom useFetch composable with pre-defined default options.
`createUseFetch` creates a custom [`useFetch`](/docs/4.x/api/composables/use-fetch) composable with pre-defined options. The resulting composable is fully typed and works exactly like `useFetch`, but with your defaults baked in.
`createUseFetch` is a compiler macro. It must be used as an **exported** declaration in the `composables/` directory (or any directory scanned by the Nuxt compiler). Nuxt automatically injects de-duplication keys at build time.
## Usage
```ts [app/composables/useAPI.ts]
export const useAPI = createUseFetch({
baseURL: 'https://api.nuxt.com',
})
```
```vue [app/pages/modules.vue]
```
The resulting `useAPI` composable has the same signature and return type as [`useFetch`](/docs/4.x/api/composables/use-fetch), with all options available for the caller to use or override.
## Type
```ts [Signature]
function createUseFetch (
options?: Partial,
): typeof useFetch
function createUseFetch (
options: (callerOptions: UseFetchOptions) => Partial,
): typeof useFetch
```
## Options
`createUseFetch` accepts all the same options as [`useFetch`](/docs/4.x/api/composables/use-fetch#parameters), including `baseURL`, `headers`, `query`, `onRequest`, `onResponse`, `server`, `lazy`, `transform`, `getCachedData`, and more.
See the full list of options in the [`useFetch` documentation](/docs/4.x/api/composables/use-fetch#parameters).
## Default vs Override Mode
### Default Mode (plain object)
When you pass a plain object, the factory options act as **defaults**. Callers can override any option:
```ts [app/composables/useAPI.ts]
export const useAPI = createUseFetch({
baseURL: 'https://api.nuxt.com',
lazy: true,
})
```
```ts
// Uses the default baseURL
const { data } = await useAPI('/modules')
// Caller overrides the baseURL
const { data } = await useAPI('/modules', { baseURL: 'https://other-api.com' })
```
### Override Mode (function)
When you pass a function, the factory options **override** the caller's options. The function receives the caller's options as its argument, so you can read them to compute your overrides:
```ts [app/composables/useAPI.ts]
// baseURL is always enforced, regardless of what the caller passes
export const useAPI = createUseFetch(callerOptions => ({
baseURL: 'https://api.nuxt.com',
}))
```
This is useful for enforcing settings like authentication headers or a specific base URL that should not be changed by the caller.
## Combining with a Custom `$fetch`
You can pass a custom `$fetch` instance to `createUseFetch`:
```ts [app/composables/useAPI.ts]
export const useAPI = createUseFetch(callerOptions => ({
$fetch: useNuxtApp().$api as typeof $fetch,
...callerOptions,
}))
```
The **function signature** (override mode) is required here so that [`useNuxtApp()`](/docs/4.x/api/composables/use-nuxt-app) is called in the setup context (at the composable call site) rather than in the module scope, where no Nuxt instance is available.
---
- [Source](https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/composables/fetch.ts)