Eligius.

Eligius was a Bitcoin mining poolMining poolA group of miners who share the work of finding blocks and split the rewards, so each gets paid steadily instead of rarely. that Luke Dashjr, a Bitcoin Core developer, opened on 27 April 2011. Mining with computer graphics cards was just taking off, and as it grew harder, he later wrote, “miners needed to work together if they were going to have any regularity in payouts.” He ran the pool his own way. Miners needed no account, only a Bitcoin address to use as their name, and Dashjr chose which transactions went into its blocks by his own rules, which from the first day accepted some unusual kinds of transaction that most of the network wouldn’t pass on. In October 2012 he handed the pool to Jason Hughes, a software engineer known online as wizkid057, who wrote that Dashjr had “many many things on his agenda which, in my opinion, are more important than the day to day maintenance of running a mining pool”.

Eligius almost never held its miners’ money. When it found a block, it paid each miner whose earnings had passed a small minimum straight from the reward, in the block’s first transaction, known as the coinbase transactionCoinbase transactionThe first payment in every block, created by its miner. It has no inputs and pays out the block reward.. So one Eligius block could pay dozens of addresses at once: block 289,996, in March 2014, paid 144. These are the miners’ shares of the reward, separate from the transactions confirmed inside the block. Dashjr later recalled the “loyal users who appreciated the transparency and non-custodial payout system of Eligius”, and contrasted it with pools that “operate like custodial bank accounts”, holding their miners’ coins. From September 2016 its blocks paid one or two addresses instead, and from 2017 the pool paid its miners in separate transactions.

Eligius was busiest in early 2014, and that June it went public with a risk, Hughes wrote, “inherent in how Bitcoin pooling works”. Pools pay their miners for near-misses, small pieces of work that show how hard each is working, while waiting for one of them to find a winning block. On 13 June, the day GHash.IO was reported to have half of all mining power, Hughes announced that two addresses had been sending Eligius near-misses but throwing away any winning block, which he called a block withholding attack.

He put the pool’s loss at about 300 bitcoin, said he had held back about 200 bitcoin of their earnings, and wrote that their owner had threatened “putting a 200 BTC bounty on hacking Eligius”. Ittay Eyal and Emin Gün Sirer, computer scientists at Cornell University, wrote that the attacker gained nothing, so the only sensible explanation was “a competing miner” trying to drive Eligius’s miners away. Others later doubted it was deliberate: in 2015 the operator of BitMinter, another pool, wrote that, last he had heard, the miner was believed to have “made their own mining client” and the withholding was “a bug, not an intended feature”.

When BTC Guild closed in 2015, its operator still recommended Eligius as a “long standing pool with good reputation”, but by 2016 Eligius was small, and in 2017 it found 11 blocks. Its last, 495,555, came on 22 November 2017. That month its website said “THE POOL IS FUNCTIONING NORMALLY” while the site was rebuilt, and its servers ran for almost two more years without finding another block. In September 2019 Hughes asked on the BitcointalkBitcointalkThe Bitcoin forum Satoshi Nakamoto opened in November 2009. Much of Bitcoin’s early history, from the pizza offer to Satoshi’s last post, happened there. forum whether there was still demand for such a pool: “Looking at the current mining landscape, my guess would be no”. No closure announcement has been found. When Dashjr launched OCEAN in 2023, he put Eligius’s total at 11,631 blocks, wrote that Hughes “had to step away and shut down the pool”, and said he was “relaunching Eligius as OCEAN”. Dashjr left OCEAN in August 2026; Hughes is now its chief technology officer.