| Material | Aluminum alloy (or steel) |
| Gate types | Solid, wiregate, locking |
| Common shapes | D, offset-D, oval, HMS/pear |
| Strength | Rated in kN along the major axis |
From the German Karabinerhaken, a spring hook used by carbine-armed soldiers to clip equipment.
A carabiner is a metal loop with a spring-loaded gate used to connect parts of a climbing system quickly and securely. Climbers use them to attach the rope to protection, build anchors, and rack gear. They come in locking and non-locking versions and in shapes optimized for different jobs.
The name comes from the German Karabinerhaken, a spring hook once used to clip a carbine rifle to a strap.
How a carabiner works
Force is designed to load the carabiner along its major axis — the long spine — with the gate closed, where it is strongest. Loading across the gate (minor axis) or with the gate open is far weaker, which is why orientation matters. Strength is stamped on the spine in kilonewtons (kN).
Types and shapes
Gates are solid, wiregate (lighter, less prone to freezing), or locking. Shapes are matched to the job: D and offset-D for general strength, oval for racking and aid, and pear-shaped HMS carabiners for belaying. Two joined by a sling form a quickdraw.
Using one safely
Keep the gate closed and load along the spine; use a locker wherever a single open gate would be dangerous. Retire any carabiner that is cracked, badly grooved, or has a sticky gate.
Frequently asked questions
What does kN mean on a carabiner?
kN stands for kilonewtons, the unit of force a carabiner is rated to hold. The numbers stamped on the spine show its strength along the major axis (spine), with the gate closed, and the weaker ratings with the gate open or across the minor axis. One kN is roughly 100 kg of force.
What's the difference between locking and non-locking carabiners?
A non-locking carabiner has a sprung gate that can be bumped open, so it is used for redundant connections like quickdraws. A locking carabiner adds a sleeve that secures the gate, and is used at single critical points such as the belay device, anchor, or rappel.
Are aluminum carabiners strong enough for climbing?
Yes. Climbing-rated aluminum carabiners typically hold 20–24 kN along the spine — far more than any fall generates — while staying light. Steel carabiners are stronger and more wear-resistant but heavier, so they are used mainly for fixed hardware and high-wear setups.
Sources
- Connector standards — UIAA
- Carabiner technical notice — Petzl