A clip-on leash attaches to the collar that the dog might already be wearing.

A leash or a lead is a rope or similar material attached to the neck of a pet (often a dog) for restraint or control. Some leashes clip or tie to collars or harnesses, while others go directly around the animal's neck.

In many jurisdictions, laws require dogs and other animals to wear leashes at all times when outdoors.

Purposes of a leash include: preventing animals from frightening or biting people or other animals, defecating and urinating in inappropriate places, endangering traffic, digging up lawns and causing other damage, and getting lost. Leashes also provide a clear method of communication and ensure control during training.

For dogs, leashes take many forms; for example:

• Very short tab leads; a clip attached to a loop handle or to a short piece of leather with a knot or similiar short handle. Allows very close, tight control of a dog in certain competition or training situations.
• Short, soft, braided leather lead with a loop handle and a clip to attach to the collar, usually about 4 feet in length, commonly used during obedience training. The softness enables the trainer to fold the leash into a shorter length and the braiding allows a firmer grip.
• Nylon webbing leash, usually 4 to 6 feet, with a loop handle and clip, most commonly used for walking dogs casually.
• Extended-length webbing leashes, 12 to 30 feet or more, usually with a loop handle and a clip, primarily for training at a distance or during tracking sessions.
• Slip-lead, usually with a loop handle and an adjustable, slipping loop at the other end that goes around the dog's neck. Often used in work or competitions—such as dog agility—where the leash must be quickly removed and replaced.
• Flexi-lead (brand name), a hook on a thin rope that retracts automatically into a large plastic handle, allowing the dog to wander 20 or 30 feet away while keeping the leash taut (in theory preventing it from tangling around obstacles or the dog's legs) but still allowing the handler to reel in the dog for closer control.