Boosted Uppercut

A boosted uppercut being performed in Sentinel Beach

Traditional

A boosted uppercut or "boosted" is a movement technique that gives Jak much more horizontal momentum than the conventional intended movement techniques, making it possible to cross larger gaps. The technique has a few methods by which it can be performed, all of which yield increased horizontal momentum:

• by slowly walking off of a ledge and pressing square, cross, circle in succession before Jak begins his falling animation;
• by running along the edge of a ledge, and then pressing square, cross, circle in succession (often called a sideways boosted);
• by standing on the very edge of a ledge so that Jak's feet point downwards, and then pressing square, cross, circle in succession;
• In Jak and Daxter: The Precursor Legacy only, by zoom walking off of a ledge, then cancelling the goggles with triangle and quickly pressing square, cross, circle in succession.

Boosted uppercuts can be performed in Jak and Daxter: The Precursor Legacy, Jak II, and Jak 3.

Technical

When Jak walks off a ledge, he enters a collision mode called low-coverage. When in this mode, Jak's surface is changed to edge-surface which has lower than normal friction. Performing a punch uppercut while in this low friction mode results in a lot more horizontal distance than with normal friction.

Note that this is also why ice boosteds, or super boosteds, work. The friction value on ice is even lower. However, if you fall off an edge of ice, you'll get switched back to edge-surface and get a normal boosted uppercut instead.

Discovery

The Backwards Boosted Uppercut was the first variant of the Boosted Uppercut to be discovered. Backwards Boosted Uppercuts regularly occur in casual play which makes it impossible to determine when it was first performed. A speedrunner named Meggachilly discovered the Boosted Uppercut that is still used in Jak and Daxter speedruns today.

TLF Boosted

There is a movement technique in Jak and Daxter: The Lost Frontier that is similar to a boosted uppercut, but is not entirely the same. By uppercutting off of a ledge and rotating the camera, Jak is able to gain more horizontal distance than intended, hence why it is referred to as a boosted uppercut.