🗳️ The Block Size War
Bitcoin's governance stress test — and who actually won it.
Start the interactive lesson →
Nearly split apart
From roughly 2015 to 2017, Bitcoin nearly split apart over a single technical question:
how big should a block actually be?
The disagreement
As Bitcoin grew more popular, its limited block size meant transactions sometimes competed for space, and fees rose.
One camp argued for the obvious fix: make blocks bigger to fit more transactions.
The counter-argument
Another camp argued bigger blocks would make it harder for regular people to run their own nodes.
Bigger blocks mean more storage, more bandwidth, more cost — concentrating power among fewer, larger operators, and undermining the decentralization that made Bitcoin worth using at all.
Cheaper transactions, bought with a more centralized network. That was the real trade being argued over.
Years of standoff
Various proposals were floated — bigger-block software like Bitcoin XT and Bitcoin Classic, and a "SegWit2x" compromise backed by many companies.
None could get the whole network to agree.
Years passed. It got genuinely ugly.
How it resolved
In August 2017, Bitcoin activated a change called SegWit through broad community consensus.
A separate group that wanted bigger blocks immediately split off, creating a new, separate asset called Bitcoin Cash.
The SegWit2x compromise itself was cancelled that November for lack of support.
Why it matters
Not even large companies and prominent developers, working together, could force a change onto the network without broad agreement from node operators and users.
Bitcoin's rules bent to consensus — not to the largest players in the room.
Anyone who disagreed was free to leave and start their own chain. Several did. The network kept going.
Try it: Who decides?
Four attempts to change the rules. Work out who actually has to agree.
A corporate coalition, a mining majority, the biggest exchange in the world, and a change nearly everyone wants. Work out who can actually make a rule change stick — the answer is the same every time, and the last case shows it doesn't mean "nothing can change." Open the Who Decides? tool →
Quick check: What was the core disagreement in the block size war?
- Whether to increase block size for more transactions, or keep it small to protect decentralization ✓
- Whether to raise the 21 million supply cap
- Which country should host the most miners
Throughput on one side, the ability of ordinary people to verify the rules themselves on the other.
Quick check: What ultimately happened when the network couldn't fully agree?
- A committee took a binding vote
- The network split — Bitcoin activated SegWit, and a separate group launched Bitcoin Cash ✓
- The change was forced through by the largest mining pools
Nobody was overruled and nobody was trapped. The dissenters left and built their own chain — which is exactly the escape hatch a permissionless system is supposed to have.
Next up
Bitcoin's rules held up under pressure.
Its exchanges did not always fare as well.