You cannot tell by looking at an egg before incubation whether it was fertilized
A fertilized egg usually looks and tastes the same as an unfertilized egg
The only reliable way to tell is by incubating the egg and checking for embryo development
After 3 to 7 days of incubation, candle the egg with a bright light
A fertilized egg may show blood vessels or a dark embryo spot when candled
An unfertilized egg usually appears clear or only shows a yolk shadow
A fertilized egg can also be confirmed by cracking it open and looking for a small white bullseye on the yolk
The bullseye does not guarantee development, but it indicates the egg was fertilized
Store-bought eggs are usually unfertilized unless labeled otherwise
If you want to know for sure, use candling during incubation or consult a poultry expert