Webs are a stationary hazard that drastically reduce the movement speed of Spelunkers and Hired Hands attempting to pass through them. Unlike most other monsters, Spiders, Hanging Spiders, and Giant Spiders can pass through Webs freely. They are usually found in tight spaces and passageways, or underneath Hanging and Giant Spiders. Webs can also be produced by Giant Spiders and the Web Gun.
For more specific information on the appearance and function of Webs in the Spelunky series, see the pages below.