Slacklining is a practice in balance that typically uses 1 inch nylon webbing tensioned between two anchor points. Slacklining is distinct from tightrope walking in that the line is not held rigidly taut (although it is still under some tension); it is instead dynamic, stretching and bouncing like a long and narrow trampoline. The line's tension can be adjusted to suit the user and different types of webbing can be used to achieve a variety of feats. The line itself is flat, due to the nature of webbing, thus keeping the slacker's footing from rolling as would be the case with an ordinary rope. The dynamic nature of the line allows for impressive tricks and stunts.

A slackline is commonly constructed with three sections of one-inch webbing: a long section of webbing (30–100 feet) strung tightly and connected to the two shorter sections (8–12 feet) that are called "tree slings" and are used as anchors on either end. The most difficult and widely discussed element of a slackline setup is the tensioning system. Common setups include simple friction methods, using wraps of webbing between two carabiners, a ratchet, a comealong, a carabiner pulley system, a roped pulley system, or a commercial slackline kit.