I’ll tell you up front, the point of this is going to boil down to if you have a lot of data to spare, it’s great and if you don’t, well, it might not be. But we’ll go through it anyway.

Apple’s new mobile operating system, iOS 9, has a cool new feature. It’s called Wi-FI Assist, and it’s enabled by default.

When Wi-Fi Assist is enabled, it automatically switches over to cellular data when Wi-Fi connectivity is weak. Apple products never want to let go of Wi-Fi. The signal might be terrible, but iOS will cling to any available Wi-Fi – even if it’s so slow as to render your phone a brick – so this is a welcome feature.

Unless you’re watching your data consumption.

The feature, which by design forces your phone to use more cellular data than it probably would normally, is opt-out on iOS 9 – so some people could be blowing through data and not even know it right now.

If this is you, and you want to turn it off, it’s easy. Just head to Settings > Cellular and scroll all the way to the bottom. There you’ll find the Wi-Fi Assist option.

But if you have enough data to spare, Wi-Fi Assist is a pretty cool feature and you should probably keep it enabled.