Most hylids show adaptations suitable for a tree lifestyle, including forward-facing eyes providing binocular vision, and adhesive pads on the fingers and toes. In the species that do not live in trees, these features may be greatly reduced, or absent.

Hylids mostly feed on insects and other invertebrates, but some larger species can feed on small vertebrates.

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Hylids lay their eggs in a range of different locations, depending on species. Many use ponds or puddles that collect in the holes of their trees, while others use water-holding plants. Other species lay their eggs on the leaves of vegetation overhanging water, allowing the tadpoles to drop into the pond when they hatch.  A few species use fast-flowing streams, attaching the eggs firmly to the substrate. The tadpoles of these species have suckers enabling them to hold onto rocks after they hatch. Another unusual adaptation is found in some South American hylids, which brood the eggs on the back of the female.