The Connecticut eLicense web portal is an online database that allows you to verify professional licenses issued by certain Connecticut state agencies: Department of Consumer Protection, Department of Public Health, Department of Agriculture, OEC Child Care & Youth Camp Licensing, and CAES Department of Entomology.
If you need guidance on how to use the portal, the Department of Consumer Protection has created step-by-step instructions, as well as a short video that shows you how to perform a lookup. They also offer a useful discussion on the Difference Between a License, Registration, and Permit.
And for more information on which state agency is (or isn't) responsible for a profession's licensing and regulation, see the DCP's comprehensive A-Z Information Index.