The safety capsule is a major element on the Norfair stage in Super Smash Bros. Brawl and Super Smash Bros. for Wii U. From time to time, a large lava wave will appear from the background and approach the stage. The damage this wave causes can be fatal to fighters depending on their damage level. To help fighters survive, a safety capsule will appear on any of the five platforms, which will move apart to accommodate the capsule if necessary. The capsule resembles a double-sided Blue Door in its Super Metroid appearance. The doors can be opened by attacks, and as the lava engulfs the stage, the doors shut. The capsule disappears afterward until the lava wave returns.
The safety capsule is not always the safest option, nor is it necessary to survive. Fighters can be damaged if hit by attacks under the platform the capsule is situated on, and some moves can allow the fighters to avoid the lava wave outside the safety capsule. For example, characters with multiple jumps can jump over the wave, or if they have a counter they can use that move to stay alive.