Bitcoin mining is undergoing a fundamental shift, as evidenced by yesterday’s mining of the largest sized block yet. Last night’s (UTC time) record-breaking block (#505,225) came in at 2.18MB. Such sizes continued overnight, with several blocks recording sizes in excess of 2MB.

The initial record was in fact short-lived, with block #505,253 – totalling 2.22MB – mined in the early stages of Sunday.

For blocks of such size, it was interesting to note that their amount of transactions – 225 and 252, respectively – were well below the average number of transactions per block (~2,000). This is indicative of large consolidation transactions; as evidenced by the many transactions with 200 inputs and 1 output, such as this one.

These growing block sizes are helping reduce the mempool size; a source of untold amounts of debate among crypto enthusiasts, developers, and miners, given it poses as a major roadblock against a societal adoption of Bitcoin.

The mempool represents the aggregate size of transactions that are awaiting confirmation. The higher it goes, so too do transaction fees paid to miners – all whilst the time taken to approve a transaction lengthens.

With Bitcoin reaching the public psyche in recent months, a mempool backlog ensued. This is hurting Bitcoin’s claim as a legitimate means of transaction; deterring retailers, customers, and financial institutions from adopting it as a payment method.

Block sizes have slowly been increasing ever since the Segregated Witness (SegWit) soft fork was activated on the Bitcoin network last year (August 24; block #481,824). Strictly speaking, the controversial 1MB block size limit – as outlined in Satoshi Nakamoto’s 2008 whitepaper – remained.

The decision not to up the block size angered many, giving rise to the Bitcoin Cash (BCH) hard fork (with 8MB block size limits) – prioritising Bitcoin’s use as a transactional currency.

SegWit introduced the concept of block weight, which can reach a maximum size of 4M weight units; making the maximum block size nearly 4MB in theory (but 1.6-2MB is more probable). Note, by stripping witness data, the block size still appears valid (i.e. under 1MB) to a non-SegWit/un-upgraded node.

The proportion of transactions using Segregated Witness remains very low at ~11 percent. However, there are many companies and software projects preparing to deploy SegWit, which will push the average block size up toward 2MB.

The news comes a week after the declaration that 80 percent of Bitcoin’s supply limit had been mined. You won’t see the supply entirely mined during this century, however, due to an impending series of ‘halvenings’ and rising difficulty.

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