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Bitcoin’s mempool was recently cleared on February 1, 2025. This is a very rare event to occur in Bitcoin. The last time this happened was on April 22, 2023. In the early days of Bitcoin, this was a common occurrence, but as the network has grown, instances of the mempool fully clearing have become increasingly rare. So, what exactly is the mempool, why does it matter, and how can Bitcoin users take advantage of these moments?
What Is the Bitcoin Mempool?
The mempool (short for “memory pool”) is where unconfirmed Bitcoin transactions wait to be included in a block by miners. When a Bitcoin user sends a transaction, it doesn’t immediately get recorded on the blockchain. Instead, it first enters the mempool, where it sits until a miner picks it up, includes it in a block, and confirms it.
Each Bitcoin node has its own version of the mempool, keeping track of transactions that haven’t yet been confirmed. The mempool serves as a kind of waiting room for Bitcoin transactions, and during times of high activity, it can become congested, leading to higher transaction fees as users compete to get their transactions confirmed faster.
Why Does the Mempool Fill Up?
Bitcoin’s block space is limited, with each block having a maximum size of around 4 MB. This means only a certain number of transactions can be confirmed every 10 minutes. When there’s more demand for transactions than the available block space, the mempool fills up, and fees rise as users prioritize their transactions.
During periods of low network activity, however, transactions clear faster, fees drop, and the mempool can fully empty. This is what happened recently—a rare occurrence in the modern Bitcoin era. Below is a graph of the mempool size, notice how very rarely in recent years does it go down to zero:
Source: Johoe’s Bitcoin Mempool Statistics
The Early Days: Why the Mempool Used to Clear Regularly
In Bitcoin’s early years, network usage was much lower, and transactions were less frequent. Since fewer people were competing for block space, miners could include all pending transactions in blocks, clearing the mempool often.
However, as Bitcoin gained adoption and more users started transacting, network activity surged. With the rise of exchanges, business adoption, and NFTs (via Ordinals), demand for Bitcoin transactions has remained high, making it increasingly rare for the mempool to fully clear.
Why the Mempool Clearing Matters
When the mempool clears, all pending transactions get confirmed, and for a brief moment, transaction fees can drop to their lowest levels. This presents a unique opportunity for Bitcoin users to take advantage of lower fees.
Key actions to consider when the mempool clears:
- Consolidating UTXOs – If you have multiple small unspent transaction outputs (UTXOs), a mempool clearing event is a great time to consolidate them into fewer, larger outputs at a low cost. This helps reduce future transaction fees when you need to spend your Bitcoin.
- Opening Lightning Channels – Lightning Network users can take advantage of low fees to open new channels cost-effectively, ensuring cheaper transactions in the future.
How Transaction Fees Work
Bitcoin transactions are prioritized based on fee per byte. Since each transaction varies in size (depending on inputs, outputs, and signatures), miners prioritize those offering the highest fee per byte.
When the mempool is congested, users must increase their fees to ensure timely confirmations. However, when the mempool is empty, transactions can be confirmed with minimal fees, sometimes as low as 1 sat/vByte—the lowest possible fee on the Bitcoin network.
Conclusion: Making the Most of Mempool Clearing Events
Understanding the Bitcoin mempool is crucial for optimizing transaction costs and efficiency. When the mempool clears, it provides a brief but valuable window for Bitcoin users to consolidate UTXOs, open Lightning channels, and execute low-fee transactions.
As Bitcoin continues to evolve, keeping an eye on mempool activity and understanding fee dynamics will be increasingly important. Whether you’re an individual user or a business, taking advantage of these rare events can lead to significant cost savings and more efficient Bitcoin usage. When the mempool is congested, and people are paying high transaction fees, it pays to be a bitcoin miner. Book a call now to purchase your first fleet.
The next time the mempool clears, be ready—it might not happen again for a long time!
Disclaimer: The information provided in this blog is for informational and educational purposes only and should not be construed as financial advice. Please consult with a financial advisor or conduct your own research before making any financial decisions.
