Bitcoin's Mempool Congestion: Unconfirmed Transactions Approach 700,000 in September

Over the last fortnight, the quantity of unconfirmed bitcoin ($BTC) transactions has consistently exceeded the 500,000 mark, nearly touching 700,000 on September 6, 2023. Metrics indicate that Bitcoin’s mempool, a shortened term for “memory pool,” has not completely cleared in more than four months, dating back to April 22, 2023.

Bitcoin’s Backlog Swells: Unconfirmed Transactions Continue to Grow

The Bitcoin network has experienced a substantial increase in transaction volume this year, surpassing previous records. This surge is attributed to the inclusion of Ordinal inscriptions alongside financial transactions processed on the network. The 31 million Ordinal inscription transactions have even surpassed the quantity of financial transactions completed in recent periods. Consequently, this trend has resulted in a notable backlog of unconfirmed $BTC transactions stuck in the mempool. On September 15, 2023, there’s 513,652 unconfirmed transfers waiting for miner confirmation.

Essentially, the mempool denotes the assembly of unconfirmed transactions awaiting inclusion in a block. When a $BTC transaction commences, it is not immediately added to the blockchain. Instead, it initially enters the mempool, where miners subsequently choose transactions from the backlog for confirmation and inclusion in the forthcoming block. Typically, bitcoin miners make their selections from the mempool based on the fee rate, i.e., the fee per byte of transaction data. Transactions with higher fees are typically given priority, as they present greater incentives for miners.

Johoe’s Bitcoin Mempool Statistics over the past six months. Screenshot recorded on September 15, 2023.

Since April 22, 2023, the backlog of unconfirmed transactions has consistently increased and has not been completely resolved since that date. During the initial two weeks of September 2023, the count of unconfirmed transactions has consistently exceeded 500,000. To effectively clear the mempool, bitcoin miners would need to confirm a total of 196 block rewards, equivalent to approximately 376 megabytes of block space. Considering that each block requires 10 minutes for mining, it would take $BTC miners approximately 32 hours and 40 minutes to process and clear the 196 blocks.

On September 6, 2023, the backlog reached a peak, with over 652,000 unconfirmed transactions recorded on that day. The increased transaction volume this year has led to all-time highs in daily confirmed transfers. For example, on May 1, 2023, approximately 682,281 transactions were confirmed. Just nine days later, on May 10, 671,668 transfers were confirmed, marking it as the second-largest day on record. The fifth-largest daily confirmation rate occurred on September 5, 2023, with miners confirming 625,257 transfers.

Although the backlog has not been fully cleared, transfer fees have remained relatively low given the circumstances. Currently, as reported by bitinfocharts.com, the average transaction fee is 0.000053 $BTC, which is approximately $1.42 per transfer. On September 15, 2023, a median-sized fee on the Bitcoin network stands at 0.000018 $BTC, or around $0.48 per transfer. Addressing the issue of unconfirmed transactions and mempool congestion in the Bitcoin network can be intricate, and as of 2023, there is no one-size-fits-all solution. Nevertheless, various strategies and improvements have been proposed and implemented over the years to tackle these challenges.

These solutions encompass utilizing Segregated Witness (Segwit), harnessing layer two (L2) concepts such as the Lightning Network, optimizing transaction size, and employing transaction batching. Nevertheless, despite the availability of these solutions for several years, the backlog has not shown signs of improvement. It is important to highlight that significant alterations to the Bitcoin protocol typically necessitate consensus among network participants, and this can be a time-consuming process.

What do you think about the backlog of unconfirmed transactions? Do you think the mempool will clear at some point? Share your thoughts and opinions about this subject in the comments section below.