Segregated Witness (SegWit) has reached its lock-in threshold. The long-debated scaling upgrade reached the necessary threshold to "lock in" today at block 479,707 with 100% of bitcoin mining pools signaling support for the proposal. According to network data, the block was mined by BitClub. But the change won't officially lock-in until tomorrow, once the signaling period has ended. Further, the change will be unusable, as CoinDesk described in more depth, for a couple more weeks. The network will move into a roughly two-week "grace period," to give users and mining pools a chance to upgrade their software. After that, which looks to end August 21, SegWit will activate and miners will start rejecting blocks that do not support the change. First proposed by bitcoin developer Pieter Wuille in December 2015, the expectation for SegWit is that it will open up several ways to scale bitcoin to support more users. While this doesn't seem particularly contentious, it has been the subject of tireless debate within the bitcoin community. Other communities such as litecoin managed to activate it last spring. But today, the SegWit loop has been closed for bitcoin.