An Extension Chip is a type of Battle Chip that links two Plug-in PETs together through a cable. When the Extension Chip is slotted into the receiving PET, the giver connects their jack-in cable to it, and their NetNavi turns into data and merges with the receiver's Navi, allowing that Navi to gain traits and abilities of the Navi providing the extension. These chips are only seen working when MegaMan.EXE is in ElecTeam Style, allowing him to gain a weapon or ability of the other NetNavi. Double Soul, an ability MegaMan gains after he loses the ability to Style Change, seems to be an evolution of ElecTeam Style and the Extension Chip, giving MegaMan most of the abilities and powers of the Navi along with a new appearance.
- Of the six extensions used, three of them become Double Souls (Roll Soul, Wood Soul, and Knight Soul) for MegaMan in the video game series, however, he only receives Roll Soul and Wood Soul in the anime.
- KnightMan and Roll's Extension Chips use the images of their Navi Chips from the games. They may be the equivalent of them or even the chips themselves used differently, although the existence of Navi Chips was acknowledged in Beast+ and were never seen in use.