Little Mac leaps forward and performs a downward hook at the end of the move. The punch will be thrown before maximum distance is traveled, but can be thrown at any time during the jump by pressing the special button, as early as right after initiating the leap. If the move is used on the ground, Little Mac will be briefly intangible from frames 5-14 as he leaps, allowing him to avoid projectiles and attacks, although throwing the punch early will reduce the amount of intangibility frames given (frames 5-8). If the move is used on an incline, such as a sloped platform or the slanted edges of certain stages, Little Mac will gain noticeably more height from the jump, depending on the steepness of the slope.
Like many of Little Mac's moves, Jolt Haymaker has high knockback scaling, and can KO at 105% near the edge on the ground and in the air. The grounded version also travels a very long distance (almost half of Final Destination), making the move useful for escaping from harm or punishing enemies suffering from lag. Unlike most of Mac's other aerial moves, Jolt Haymaker keeps its power in the air, allowing it to be used as a surprise aerial KO option. It can also cause a sacrificial KO by chaining several forward aerials into a Jolt Haymaker, which can KO as early as 65% but at the risk of losing a stock.
Due to the move's wide hitbox and decent amount of lingering frames, Jolt Haymaker is one of Little Mac's few useful edgeguarding tools (apart from his down smash). It can be used to stage spike by punching an opponent against the edge should they lose their edge invincibility, and its power makes this deadly on stages with slanted ledges such as Battlefield.
This move is Little Mac's only reliable horizontal recovery move, as Slip Counter only gives distance if it counters an attack, while a fully-charged Straight Lunge takes too long to charge. However, it is notably poor at doing so compared to other recovery moves, as it grants purely horizontal momentum, loses its intangibility in the air and travels half the distance (which was decreased further in Update 1.0.4). Additionally, it travels even less distance if Mac's fist is swung early, and does not automatically ledge snap until the move's animation is complete. This makes it very possible for Mac to get KOed at a distance where other fighters would be able to recover from, and he is also vulnerable to being knocked off or meteor smashed even if he manages to get to a ledge, a weakness shared with his other recovery move Rising Uppercut.
Another weakness of Jolt Haymaker is its inability to stop at the edge, similar to Fox Illusion in Melee. On the ground, Little Mac keeps all his forward momentum even if he swings his fist during the first few frames. This makes it extremely risky to use on small platforms or near edges, as players can easily underestimate the distance Little Mac jumps, easily sending him flying offstage. In SSB4, this results in a self-destruct, since the move renders him helpless, but in Ultimate, this was changed such that Mac no longer enters freefall after the move and can potentially recover with Rising Uppercut, significantly improving its utility and allowing it to be used as a reliable edgeguarding tool. A way to circumvent the former occurrence is to do a quick short-hop if attempting this near edges, making combos such as a down tilt to aerial Jolt Haymaker much safer.
Like most of Little Mac's special moves, Jolt Haymaker has a unique 8-bit sound if he is using a Wireframe alternate costume.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
The Jolt Haymaker has no direct origin in Little Mac's abilities in the Punch-Out!! games. However, one of the series' recurring opponents, Von Kaiser, uses a similar jumping overhead punch in his Title Defense match in Punch-Out!! on Wii, which would knock out Little Mac in one hit if not dodged. Nick Bruiser, the final boss of Super Punch-Out!! on SNES, also uses a similar jumping overhead punch. The move's name may be based on its ability to "jolt" Little Mac forward with high speed while attacking.