A freckle is an usually high deposit of melanin on one spot in the skin — so it seems the middle of women's wrists is a popular spot for the pigment.
Exposure to the sun activates the production of more melanin, which can cause freckles to be darker. Areas like the wrist are often exposed to sunlight.
Most women who posted a picture were shocked after discovering the freckle on their wrist and that so many other people had it.
"I was like 'nah' but apparently I keep my wrist freckle under my watch," one person wrote.
Another wrote: "I was like not me. Then I looked at my left wrist."