BIP 148, BIP 141, BIP 91 …

A number of bitcoin improvement proposals (all aimed at boosting the cryptocurrency’s transaction capacity) are set to come to a head in the coming weeks, ending either in a smooth upgrade, a potentially difficult split, or maybe, simply status quo.

While it looks likely that at least one will go into effect, it’s not clear which proposal (or proposals) will trigger, meaning, for now, we’re left tracking how much support each proposal will actually get – and when.

In separate guides, we’ve covered the two main proposals, SegWit2x and BIP 148, as well as how BIP 91 looks to moderate between them.

Still, understanding how the proposals interact can be difficult.

Today, 76% of bitcoin’s mining hashrate is signaling for BIP 91. So, it looks like it could go through. But, if it doesn’t reach the necessary threshold of 80% for a period of 336 blocks by August 1, then BIP 148 will kick in, setting off a slew of ifs and whens.

To help you navigate, we’ve put together the following timeline to show the many ways the summer’s scaling drama could unravel:


  • SegWit2x (BTC1): Backed by miners and startups, this proposal seeks to enact SegWit via a soft fork, while committing to a block-size increase by hard fork three months later.
  • Segregated Witness (SegWit): Proposed by volunteers of Bitcoin Core in 2015, SegWit is aimed to increase network capacity and solve transaction malleability via a soft fork. BIP 141, its proposal, requires a super-majority (95%) of miners to signal for the upgrade over two weeks.
  • BIP 91: Created by BitmainWarranty engineer James Hilliard, BIP 91 looks to lock-in SegWit2x’s SegWit update before August 1, making the proposal compatible with BIP 148. BIP 91 requires 80% of bitcoin’s miners to signal support for a lock-in and a shorter signaling period than BIP141.
  • BIP 148: Uses an older mechanism for making changes to bitcoin, called a user-activated soft fork (UASF). It requires about 50% of mining pools to support the change. Without that support, BIP 148 could activate and split the network into two competing blockchains.
  • Bitcoin ABC: A version of the bitcoin client that erases SegWit and enables a dynamic block size. It was first proposed in reaction to the idea of a UASF, which has some opposition in parts the industry. If bitcoin splits because of UASF BIP 148, the Bitcoin ABC client will launch on another chain.

Disclosure: CoinDesk is a subsidiary of Digital Currency Group, which helped organize the SegWit2x agreement.

Code image via Shutterstock

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