Crack the egg open and look for a small white bullseye-like spot on the yolk
A fertilized egg may show a more distinct germinal disc than an unfertilized egg
Before incubation, fertilized and unfertilized eggs usually look the same from the outside
Candle the egg with a bright light to check for developing veins or an embryo after incubation has started
Look for visible blood vessels or dark embryo growth during incubation
If the egg has been incubated for several days, a fertilized egg may show signs of development when candled
An unincubated egg cannot be reliably identified as fertilized by appearance alone