IOS - remove ALL padding from UITextView

Although it is iOS 7 only, an extremely clean solution is to set the textView's textContainerInsets as such:

[textView setTextContainerInset:UIEdgeInsetsZero];
textView.textContainer.lineFragmentPadding = 0; // to remove left padding

This will effectively remove all padding (insets) around the text inside the text view. If your deployment target is iOS 7+ then this is the best solution thus far.

For iOS 11.7

Following code worked for me:

    textView.textContainer.lineFragmentPadding = CGFloat(0.0)
    textView.textContainerInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    textView.contentInset = UIEdgeInsets(top: 0,left: 0,bottom: 0,right: 0)

From the Official Documentation:

textContainerInset : It is possible to set the text container and view sizes and resizing behavior so that the inset cannot be maintained exactly, although the text system tries to maintain the inset wherever possible.

In any case, the textContainerOrigin and size of the text container are authoritative as to the location of the text container within the view. The text itself can have an additional inset, inside the text container, specified by the lineFragmentPadding method of NSTextContainer.

To completely remove all padding, the lineFragmentPadding must be taken into account.

let padding = textView.textContainer.lineFragmentPadding
textView.textContainerInset =  UIEdgeInsets(top: 0, left: -padding, bottom: 0, right: -padding)

The lineFragmentPadding default value is 5, and is at the beginning and end of fragment rectangle.

Some answers suggested setting lineFragmentPadding to 0. However, as per discussed in the doc, it is not designed to express text margins. So do not set it to 0.

Swift 4 version for the OA

self.tDescription.textContainerInset = UIEdgeInsets.zero
self.tDescription.textContainer.lineFragmentPadding = 0