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# Set Next Base Fee \[block.setNextBaseFeePerGas]

Sets the next block's base fee per gas.

## Usage

This example sets the next block's base fee per gas.

:::code-group
```ts twoslash [example.ts]
import { client } from './viem.config'

await client.block.setNextBaseFeePerGas({
  baseFeePerGas: 1_000_000_000n,
})
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
import { Client, http, testActions } from 'viem'
import { anvil } from 'viem/chains'

export const client = Client.create({
  chain: anvil,
  transport: http(),
}).extend(testActions())
```
:::

### Standalone Action

Call `Actions.block.setNextBaseFeePerGas` directly by passing the Client as the first argument.

:::code-group
```ts twoslash [example.ts]
import { Actions } from 'viem'
import { client } from './viem.config'

await Actions.block.setNextBaseFeePerGas(client, {
  baseFeePerGas: 1_000_000_000n,
})
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
import { Client, http } from 'viem'
import { anvil } from 'viem/chains'

export const client = Client.create({
  chain: anvil,
  transport: http(),
})
```
:::

## Return Value

`void`

No value is returned.

## Parameters

### baseFeePerGas

* **Type:** `bigint`

The base fee per gas (in wei) to set.

```ts twoslash
import { Actions, Client, http } from 'viem'
import { mainnet } from 'viem/chains'

const client = Client.create({
  chain: mainnet,
  transport: http(),
})
// ---cut---
await Actions.block.setNextBaseFeePerGas(client, {
  baseFeePerGas: 1_000_000_000n, // [!code focus]
  mode: 'hardhat',
})
```

### mode

* **Type:** `'anvil' | 'hardhat' | 'ganache'`
* **Default:** `'anvil'`

The test node implementation to target.

```ts twoslash
import { Actions, Client, http } from 'viem'
import { mainnet } from 'viem/chains'

const client = Client.create({
  chain: mainnet,
  transport: http(),
})
// ---cut---
await Actions.block.setNextBaseFeePerGas(client, {
  baseFeePerGas: 1_000_000_000n,
  mode: 'hardhat', // [!code focus]
})
```