# sleep

## Function

Let the current thread sleep for the specified number of milliseconds.

## Syntax

```bt
sleep(millis)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| millis | Int | No | 0 | The number of milliseconds to sleep; negative numbers are treated as 0. |

## Return value

| Type | Description |
| ------ | ------ |
| Empty | Return to Empty after sleeping. |

## Example

```bt
result = sleep(1)

// Output: Empty
echo(type(result))
```

## Notes

- This function blocks the current execution flow.
- Short `sleep()` is allowed in Web requests, but the number of dormant milliseconds cannot exceed `BT_IO_TIMEOUT_MS`, the default is 30000 milliseconds; the entire request script will enter the blocking pool to avoid blocking Tokio Web workers.
- The complete rules in web requests are found in: [Web Blocking API Policy](/en/docs/web/io-policy).