Between 2015 and 2017, the community split over how to scale.
The two paths
- Bigger blocks: raise the block size limit so more transactions fit on-chain.
- Layers: keep blocks small so ordinary people can run a full node, and scale with SegWit and the Lightning Network.
How it ended
- Bitcoin Cash split off with a hard fork after block 478,558 on 1 Aug 2017.
- SegWit activated at block 481,824 on 24 Aug 2017, after pressure from the BIP 148 user-activated soft fork.
- The SegWit2x plan to double the block size was cancelled on 8 Nov 2017, before its fork.
What it proved
Large companies and many miners backed SegWit2x, yet it did not happen. Users running nodes decided which rules they would accept. That is Bitcoin's answer to "who controls it?": no coalition can change the rules without the users.
Scaling continued in layers, and Bitcoin kept the property that a home computer can verify everything.