Bitcoin
The original chain — SegWit, 1 MB base block weight, UASF victory.
Bitcoin (BTC) is the chain that continued after the 2017 block size wars. While big-block advocates forked away, the majority of developers, exchanges, and node operators stayed on the path defined by Segregated Witness and conservative on-chain scaling.
SegWit activated in August 2017 at block 481,824, increasing effective capacity to roughly 2–4 MB through witness data discounting and fixing transaction malleability. The UASF (User-Activated Soft Fork) movement had threatened to reject non-SegWit blocks, forcing miners to signal BIP 91 and lock in the upgrade.
BTC retained the SHA-256 proof-of-work algorithm, the 21 million supply cap, and the ossified development culture that treats consensus changes with extreme caution. Layer-two scaling via the Lightning Network became the preferred path for payments, while base-layer blocks remained deliberately scarce.
Outcome
Dominant chain — highest hash rate, liquidity, and developer activity. Treated as the canonical Bitcoin by virtually all major exchanges and institutions.
Key Figures
Key Blocks
Primary Event
SegWit ActivatesRelated Events
UASF Movement Gains Momentum
Users threaten to reject non-SegWit blocks.
BIP 91 Locks In — SegWit Path Cleared
Miners signal overwhelming support for SegWit activation.
SegWit Activates
Segregated Witness goes live at block 481,824.
Bitcoin Cash Hard Fork
Contentious fork creates Bitcoin Cash at block 478,558.