A typical Flea is about 3mm long. They are dark brown to black in colour. In a typical infestation there will be several Fleas that would be seen jumping on and off people and their pets. The presence of Fleas does not remain doubtful for long as their nature is very aggressive and in your face kind 😟.
Notice that this blood sucking parasite insect has very strong rear legs that allow it to jump as much as 13 inches forward (about 110 times it’s length) or 7.75 inches high ⚠️.
The second image shows a dead Flea on a 10 ¢ Canadian coin for comparison.