Lava walk is a movement technique that allows Jak to walk in pools of lava without dying. It can only be performed in Jak and Daxter: The Precursor Legacy.
A lava walk can be performed by grabbing a ledge in such a way that Jak is half in the lava, followed by letting go of the ledge. On PS2, PS3, and PS4, the lava walk will stop working and Jak will instantly die if any action other than simple walking or running is performed while in the lava. It is possible, however, to jump out of the lava without dying. Performing a lava walk while on 1 health point will cause the ghost glitch to activate.
Historically, lava walks in Volcanic Crater were discovered by various casual players and uploaded to YouTube. In the case of Mountain Pass (Klaww fight area), speedrunners theorized a lava walk to be a possible way to skip Klaww, though it took a long time for a method to be found. Eventually, speedrunner Piggleberry found a suitable ledge grab, which was soon after used by blahpy to successfully lava walk. Not long after, Ouiji_Shi used the lava walk to successfully skip Klaww.