In the parts of tropical Africa where both species occur, the Barn Swallow can easily be confused by the very similar looking Angola Swallow.
However, the dark blue breast-band of the Angola Swallow is much thinner and incomplete in the center.
In addition, the underparts of the Angola Swallow are grey (instead of whitish in the Barn Swallow) and much shorter.

First 4 photos: Lake Mburo National Park, Uganda, 16 January 2025
5th photo: Kazinga Channel, Queen Elizabeth National Park, Uganda, 23 January 2025