On the eve of a major change in bitcoin, a threat of a split in the digital currency has been avoided — for now.

A move by users to force a change in the computer code by Monday has worked. A majority of "miners" — the core bitcoin users who verify bitcoin transactions around the world — has signaled support. Though the change is designed to improve capacity on the increasingly clogged network, some miners had objected because it could reduce transaction fees they collect.

The show of support has helped reverse a slide in the value of bitcoin from around $1,900 two weeks ago to roughly $2,800...