In Europe, the Essex Skipper (Thymelicus lineola) can easily be confused with the Small Skipper (Thymelicus sylvestris) and the Large Skipper (Ochlodes sylvanus).
The main difference with the Small Skipper is the color of the underside of the button at the end of the antennae.
The underside is black in the Essex Skipper while it is yellow-brown in the Small Skipper.
The Small Skipper is further distinguished from the Essex Skipper by the two-colored underside of the forewings and in the males the scent stripe that is not parallel to the veins.

The Large Skipper is distinguished by the light spots on the underside of the wings and, in the male, the thick black scent stripe through the center of the forewing, which is thinner in the other two.
In addition, the Large Skipper has hooks at the tips of the antennae that are very conspicuous and are not present in the Small Skipper and the Essex Skipper.

1st photo: Drentsche Aa National Park, The Netherlands, 7 July 2020
2nd & 3rd photo: Nature Reserve Vlinderdas, Ede, The Netherlands, 14 July 2021
4th & 5th photo: Zuiderheide, Laren (N-Holland), 12 July 2022