UICollectionView adds top margin

I want to put a UICollectionView control that shows thumbs horizontally (only a single line of thumbs). For some reason the UICollectionView push the thumbs 44 pixels down, so the "0" height is actually "44". I assume it might be adding this space to consider the navigation bar height (I just assume). Since my UICollectionView is only on part of the screen, I don't want this margin. Is there a way to remove it?

The issue may be in collection view's content insets. Try to add self.automaticallyAdjustsScrollViewInsets = NO; into view controller's viewDidLoad method.

You can set this in the storyboard too.

Make sure you've selected the ViewController, and then untick "Adjust Scroll View Insets".

I haven't tested what this IB/Storyboard method does on iOS6 though. With the code method you need to check that the VC responds to the method:

if ([self respondsToSelector:@selector(setAutomaticallyAdjustsScrollViewInsets:)]) {
self.automaticallyAdjustsScrollViewInsets = NO;
}

I found that adding:

self.edgesForExtendedLayout = UIRectEdgeNone;

In the view controller I was loading the UICollectionView in solved the problem as I couldn't get the accepted answer to work.

The question I found this answer to can be found here and provides an extremely in-depth and interesting explanation of the difference between automatically adjusted scrolled view insets, extended layouts and edge for extended layouts.

Well worth a read

Swift 3:

First you want to set the viewControllers automaticallyAdjustsScrollViewInsets to false:

self.automaticallyAdjustsScrollViewInsets = false

Then, you should be able to adjust the edge insets accordingly:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
    //top, left, bottom, right
    return UIEdgeInsets(top: 10, left: 0, bottom: 0, right: 0)
}