Top Secret? Bitcoin Scaling Plan Segwit2x Leaves More Questions Than Answers

While SegWit2x has significant support, according to some in the bitcoin community, the group is closing off software development to outsiders.

AccessTimeIconJun 23, 2017 at 5:20 p.m. UTC
Updated Sep 11, 2021 at 1:28 p.m. UTC
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After years of debate, the Segwit2x scaling proposal looks like it could play a role in – finally – taking bitcoin a step forward.

But the coders and companies involved have been doing at least some of the development behind closed doors, a way of working that some argue runs counter to bitcoin's value proposition as a decentralized money that no one person, or group, controls.

The project, which follows in a long line of proposals for increasing bitcoin's transaction capacity, is now supported by an all-time-high of nearly 90% of the bitcoin mining hashrate.

Since the current method of triggering major code changes relies on the support of mining pools, it seems likely that the first portion of the agreement, SegWit, will activate on the network by the end of July. (Although, it's hard to say what will happen with the rest of the proposal.)

But, while Segwit2x is perhaps the most widely-supported scaling agreement among companies and mining pools following years of debate, some have argued that key decisions are being made by an insular group of companies.

These companies, some argue, have continued pushing the proposal through even though many of the developers that are perhaps the most familiar with bitcoin's code find fault with the technical implementation and disagree with the stated goals.

And those same companies have been elusive when it comes to details about the status of the proposal itself.


Segwit2x was kick-started at an invite-only meeting comprised of big companies and large mining pools in the space.

From the beginning, one of the main criticisms levied against Segwit2x is that its development process isn't open to everyone. And many argue this process doesn't jibe with bitcoin's history of open-source development.

There is certainly evidence to the contrary. Btc1, as the Segwit2x software implementation is called, is hosted on GitHub where any developer is welcome to point out bugs and suggest improvements. This open process has indeed already led to major changes in the project's direction. Similarly, the mailing list is open for anyone in the community to at least peruse – if not post to.

In other ways, the effort is staying true to its secretive origin story.

There's an invite-only Slack group, where companies that originally pledged to contribute are represented, including Abra, Bitfury, BitGo, BitPay, Blockchain, Bloq, BTCC, Ledger, RSK Labs and Xapo.

Others included in the Slack group are OB1, Purse and developers from the alternative bitcoin implementation Bitcoin XT, which aimed to increase bitcoin's block size parameter to 8MB in 2015.

Most of these companies and individuals who have committed developer resources, though, declined to provide specific information in response to CoinDesk requests to understand their involvement. Some companies did not respond at all.

Others confirmed that they're involved in development, but declined to be more specific about which developers are involved and what they're working on.

Who and what?

"We are also contributing technical expertise to the Segwit2x code, which is in its test phase right now on a separate testnet," said Valery Vavilov, CEO of The BitFury Group.

Many company responses were similarly vague.

Yet Vavilov continued:

"We are also in the working group that is researching, building, reviewing and testing the upgrade, and will help businesses adopt the upgrade as well."

Companies are currently testing the code on the newly-deployed testnet. On Thursday, the group released a public testnet faucet, which produces fake bitcoins that developers can use.

A number of developers are tuned into the effort, as seen on the GitHub and the Segwit2x project mailing list. Those two resources make it easy to see a few of the people involved in development, including posted contributions from Bloq CEO Jeff Garzik and CTO Christopher Jeffrey.

While Digital Currency Group (DCG) CEO Barry Silbert is often viewed as the public face and linchpin of the effort (it’s often called the "Silbert Agreement"), he noted he's "not involved on the development side at all", and so can't comment on the process any more than what's already been published.

Despite knowledge of the process, there are gaps in the community's understanding of what's being developed, such as who specifically is contributing to the effort and what they are contributing.

Missing peer review?

Those who are not contributing, according to Lightening Labs CEO Elizabeth Stark, are those who have disagreed with the proposal in some way.

Stark said her company provided technical feedback to Segwit2x because they didn't agree with the proposal for "various technical reasons". And according to Stark, they were not invited to participate further.

"This proposal has like zero developer consensus," she said, referring to Bitcoin Core developers, most of whom have outright rejected the project.

She added:

"Unfortunately, the [mailing] list is only for people that agree with Segwit2x."

Again, opponents said, this philosophy contrasts with bitcoin's open development process so far, which invites all developers to contribute their ideas. A loose group of volunteer developers work on Bitcoin Core, for example, where development, for the most part, is done out in the open.

On the other hand, Segwit2x's closed approach to development "allows people to self-vindicate, and shields you from peer review and public commentary," wrote Blockstream CEO Adam Back in an email to the working group.

He continued:

"The forming of distinct and closed communication channels is not inviting review. Why would this project be special in needing to work in closed/controlled environments and not participate openly like the six or so other implementations and hundreds of developers across dozens of companies, institutions and individuals[?]"

Disclosure: CoinDesk is a subsidiary of Digital Currency Group, which has an ownership stake in Abra, BitGo, BitPay, Blockstream, Bloq, BTCC, Ledger, OB1,, RSK Labs and Xapo. 

Hands behind a blue door image via Shutterstock


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