An egg candler is a tool used to illuminate the inside of an egg, allowing you to check embryo development, fertility, and shell quality—without breaking the shell.
A bright light source (often LED) is placed against the blunt end of the egg.
The shell becomes semi-transparent, allowing you to see inside:
Embryo movement
Blood vessels
Air cell size
Cracks or defects in the shell
Purpose What to Look For
Fertility By Day 5–7: Look for blood vessels and embryo shadows
Embryo Development Watch movement and growth progress
Air Cell Monitoring Air cell enlarges as egg loses moisture—important for hatchability
Cracks/Defects Detect hairline cracks, double yolks, or rots
Egg Grading (non-incubation) Quality control before sale or consumption