---
title: DISPATCH_QUEUE_PRIORITY_BACKGROUND
framework: dispatch
role: symbol
role_heading: Global Variable
path: dispatch/dispatch_queue_priority_background
---

# DISPATCH_QUEUE_PRIORITY_BACKGROUND

Tasks run at the background priority, which is equivalent to the background quality-of-service level.

## Declaration

```swift
var DISPATCH_QUEUE_PRIORITY_BACKGROUND: Int32 { get }
```

## Discussion

Discussion Use quality-of-service constants instead. This constant maps to the QOS_CLASS_BACKGROUND class. Items dispatched to the queue run at background priority; the queue is scheduled for execution after all high priority queues have been scheduled and the system runs items on a thread whose priority is set for background status. Such a thread has the lowest priority and any disk I/O is throttled to minimize the impact on the system.

## See Also

### Priorities

- [DISPATCH_QUEUE_PRIORITY_HIGH](dispatch/dispatch_queue_priority_high.md)
- [DISPATCH_QUEUE_PRIORITY_DEFAULT](dispatch/dispatch_queue_priority_default.md)
- [DISPATCH_QUEUE_PRIORITY_LOW](dispatch/dispatch_queue_priority_low.md)