Bitcoin XT (2015) — BIP101

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In many ways, Bitcoin XT served as the prelude/buildup to the eventual Bitcoin Cash hard fork. The manifestation of the Bitcoin XT hard fork was borne out of the age-old debate in the Bitcoin community regarding scalability. As many in the community had noted as early as 2010, the usability of Bitcoin would be threatened without some tangible change to the consensus rules.

Philosophically and technically, this argument elicited a variety of different viewpoints, arguments, and criticisms. Some individuals felt that the best way to increase the scalability and usability of Bitcoin would be to increase the block size. If you used Bitcoin in December of 2017, you probably noticed that the fees were exorbitantly high. The reason for this was because there was not enough room within the blocks for miners to include all the TX that were being sent to the network. This meant that increasingly higher fees had to be paid in order to incentivize the miners to include one’s TX to be included. In some cases, TX fees needed to be in excess of $20 if one wanted a realistic opportunity to have their TX confirmed.

Many in the Bitcoin community saw the inevitability of this fate years prior. Thus, many had advocated for an increase in the block size. However, there were was a stronger segment of the community that was against such increases. This increase, they argued, would harm the stability of the network because it would reduce the # of full nodes on the network.

Why Would They Think That?

This criticism was actually noted directly in the BIP101 through the statement:

As noted earlier, only full nodes can validate blocks. By increasing the block size, one must also increase their computer/device’s memory and technical capacity. Opponents to the increase of Bitcoin’s block size argued that this increase in capacity would reduce the number of full nodes on the network, subsequently making the network less secure.

Below is an image detailing the requirements necessary to run a full node:

Proponents of the increase in block size argued that the increase in technology over time would mitigate these necessary increases in computing power and network capabilities of those who wished to run a full node.

Bitcoin XT was launched before the Bitcoin network had truly reached a boiling point on this issue.

Mike Hearn, the most outspoken advocate for the increase in block size at that time, spearheaded the Bitcoin XT movement. However, Gavin Andresen also joined forces with Mike Hearn later on and they both partnered up to develop Bitcoin XT.

Who Are Mike Hearn and Gavin Andresen?

For those unfamiliar with those two names, both Mike Hearn and Gavin Andresen were instrumental in assisting the development of Bitcoin from its earliest stages. Gavin Andresen, whom is noted for a number of things, is perhaps most famous for being the last person that Satoshi ever talked to. Before Satoshi’s departure, Gavin, in many respects was the ‘point person’ for Satoshi in the weeks prior to his eventual disappearance. After Satoshi died, Gavin also took up the torch as the de facto ‘leader’ and ended up assembling individuals that would make the first incarnation of the ‘Core’ team.

Hard Fork Rules

According to another Howtotoken article that covered this issue briefly, the hard fork rules established by Bitcoin XT was an increase in the block size from the limit (still in effect) of 1 MB to 8 MB. However there are many other notable changes were introduced within the BIP101 as well.


· “The maximum size shall be 8,000,000 bytes at a timestamp of 2016–01–11 00:00:00 UTC (timestamp 1452470400), and shall double every 63,072,000 seconds (two years, ignoring leap years), until 2036–01–06 00:00:00 UTC (timestamp 2083190400).”

· “Deployment shall be controlled by hash-power supermajority vote (similar to the technique used in BIP34), but the earliest possible activation time is 2016–01–11 00:00:00 UTC.”

· “This BIP proposes replacing the fixed one megabyte maximum block size with a maximum size that grows over time at a predictable rate.”

According to Mike Hearn in his exit article from the Bitcoin world (which had a monumental impact on the community and signaled the “blowing up” point of this argument), he initiated the Bitcoin XT hard fork for the following reasons:

The reception from the community was poor at best. Mike Hearn summarized some of this community reaction in his exit article:

Brief research provides some strong evidence that any and all dissension against any block size increasing alternatives to Bitcoin was fiercely and aggressively attacked/shunned/condemned/ridiculed/excommunicated in the community. The vast majority of these measures were implemented by Theymos (longtime member of the community since 2010, runs the Bitcoin reddit, Bitcointalk as well as Here are some examples of this censorship below:

· Theymos threatens to remove Coinbase entirely from /r/Bitcoin on Reddit as well as the bitcointalk forums if it dares support Bitcoin XT (alternative chain created by Gavin+Mike with bigger blocks to test community support for the idea).

· Petition to remove Coinbase from the ‘Choose Your Wallet’ page on GitHub for endorsing/running Bitcoin XT nodes.

· Shutting down all of the Bitcoin XT nodes.

· There is an active keyword list of words/topics/phrases that are automatically removed from the Bitcoin subreddit.

· Reddit CEOs ponder whether Theymos should be removed as moderator due to his active censorship of conflicting/competing ideas.

· More general information/dissection of Theymos’ censorship habits.

Ironically, at the time of writing, Vitalik issued a statement approximately 10–12 hours ago denouncing the censorship of different internet hubs that host Bitcoin as ‘deplorable’.

There were also multiple publications around the time of the hard fork release that reported that Bitcoin XT nodes and users were attacked en masse to disrupt the project.

However, to state that the community was devoid of support for Bitcoin XT would be inaccurate. There are numerous reports that attest to the relatively strong support behind the concept. Several corporations signaled their support for the project and many developers+miners were on board as well, in addition to Coinbase.

Without digging too much into unsupported theory, one could at least conclude that there was a segment of the Bitcoin community that not only strongly disliked the Bitcoin XT project, but possessed enough power to effectively impede the progress of Bitcoin XT.

Current Status

As you probably guessed from everything that was stated above, Bitcoin XT was effectively destroyed. At the time of writing, there are only 11 Bitcoin XT Nodes in service.

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