Bitcoin's Lowest Block Hash Values

Abstract: In this short and simple piece, we take a look at a list of the lowest block hash values in Bitcoin history. We also compare the block hash values with the difficulty target and identify blocks where the block hash was lowest relative to the necessary target. The Bitcoin block mined on 15 June 2020, at height 634,842, has the lowest ever block hash value and is also the 2nd biggest “beat”, when compared to the difficulty target.

Overview

Bitcoin’s proof of work consensus mechanism consists of miners attempting to find a block hash, for each Bitcoin block, with a low enough value to be considered valid. The block hash value must be below the difficulty target. The difficulty target automatically adjust s every two weeks or so, to ensure the expected time one needs to wait for a Bitcoin block is around 10 minutes. The block hash value must be lower than the difficulty target value. In some cases it can be a little bit lower or in other cases it can be much lower, either way it does not really matter, the block is still valid.

Bitcoins lowest block hashes

Since Bitcoin launched, the price has appreciated and efficiency of mining machines has improved, therefore the block hash values have in general been getting lower and lower as time progresses and the required difficulty increases. The below table (Figure 1), lists the ten lowest block hash values in Bitcoin’s history. As one would expect, the blocks were all produced relatively recently, in the 2019 to 2021 period.

Figure 1 - Top 10 lowest Bitcoin block hashes

Source: BitMEX Research

Note: Data up to block height 720,441

The block with the lowest ever block hash value was produced by Binance pool on 15 June 2020, at block height 634,842. The value of the block hash is 4.98 x1048(approximately the number 5 followed by 48 zeros). The hexadecimal representation of this number, which is often shown in block explorers, has 23 leading zeros. As Figure 2 below indicated, at the time of writing, this is the only ever Bitcoin block with 23 leading zeros.

Figure 2 - Number of leading zeros in Bitcoin’s block hash

Source: BitMEX Research Note: Data up to block height 720,441

Comparing the block hash value to the required difficulty target

Another interesting metric is comparing the block hash value with the required difficulty target value. In Figure 3 below, we have compared these two values in percentage terms. A valid block hash can in theory be between 0% to 100% lower than the required target difficulty. The block hash cannot be more than 100% lower than the target value, since the block hash value cannot be lower than zero. The table below lists the top 10 blocks in Bitcoin’s history, ranked by the percentage beat compared to the target difficulty (i.e. the ten closest blocks to 100%). These “lucky” blocks are relatively evenly distributed across Bitcoin’s history.

Figure 3 - Top 10 Bitcoin block hash percentage beats

Source: BitMEX Research

Note: Data up to block height 720,441

The largest beat occurred on 5 August 2015 at height 368,527. This block was mined by SlushPool and had a block hash value 99.99991% lower than the required target.

There is some overlap in Figure 1 and Figure 3, with the block at height 634,842 having the lowest ever block hash value in history and also being the 2nd biggest beat. The block at height 585,774 has the 2nd lowest ever block hash value, while also being the 6th largest beat.