On august 1st 2017, after months of the Bitcoin miners stalling an upgrade to the protocol, the Bitcoin community activated a user activated soft fork (UASF). The UASF allowed the upgrade to happen as long as a majority of the Bitcoin users enforced it.
The upgrade we are talking about is Segregated Witness, also known as SegWit, and it is an effective increase in the Bitcoin block size, allowing the Bitcoin blockchain to be able to handle more transactions. SegWit not only increases the amount of transactions Bitcoin’s blockchain can handle, but it also allows second layer solutions, like the Lightning Network.
UASF was a very important moment in Bitcoin’s History. It proved that miners do not have ultimate power over the blockchain and that users can affect the direction of Bitcoin even when it is against the miner’s interest.
The UASF worked by rejecting the bitcoins miners generated if they did not approve the upgrade. For a miner having a block rejected can be a big deal and cost thousands of dollars, for this reason all miners started voting in favour of SegWit. The UASF was a very scary moment for the people of Bitcoin, nobody was certain of what was going to happen.
The UASF was very successful for Bitcoin, it however did not leave everyone happy, people that did not went SegWit activated went on and created a new coin, based off of the Bitcoin Code, this coin is known as Bitcoin Cash.
Bitcoin cash at the time of writing is trading for less that 10% of the value of Bitcoin and has gradually been declining in value since it split from Bitcoin in August 2017