---
url: /reference/api/Function.defineConfig.md
---
# Function: defineConfig()

## Call Signature

```ts
function defineConfig(options): UserConfig
```

Defined in: [src/config.ts:10](https://github.com/rolldown/tsdown/blob/eb40c95efdf7f98d0aa7b0178a3b7322986bd419/src/config.ts#L10)

Defines the configuration for tsdown.

### Parameters

#### options

[`UserConfig`](Interface.UserConfig.md)

### Returns

[`UserConfig`](Interface.UserConfig.md)

## Call Signature

```ts
function defineConfig(options): UserConfig[]
```

Defined in: [src/config.ts:11](https://github.com/rolldown/tsdown/blob/eb40c95efdf7f98d0aa7b0178a3b7322986bd419/src/config.ts#L11)

Defines the configuration for tsdown.

### Parameters

#### options

[`UserConfig`](Interface.UserConfig.md)\[]

### Returns

[`UserConfig`](Interface.UserConfig.md)\[]

## Call Signature

```ts
function defineConfig(options): UserConfigFn
```

Defined in: [src/config.ts:12](https://github.com/rolldown/tsdown/blob/eb40c95efdf7f98d0aa7b0178a3b7322986bd419/src/config.ts#L12)

Defines the configuration for tsdown.

### Parameters

#### options

[`UserConfigFn`](TypeAlias.UserConfigFn.md)

### Returns

[`UserConfigFn`](TypeAlias.UserConfigFn.md)

## Call Signature

```ts
function defineConfig(options): UserConfigExport
```

Defined in: [src/config.ts:13](https://github.com/rolldown/tsdown/blob/eb40c95efdf7f98d0aa7b0178a3b7322986bd419/src/config.ts#L13)

Defines the configuration for tsdown.

### Parameters

#### options

[`UserConfigExport`](TypeAlias.UserConfigExport.md)

### Returns

[`UserConfigExport`](TypeAlias.UserConfigExport.md)