Question 1

What is the difficulty target?

Accepted Answer

The difficulty target is a 256-bit number that a block's hash must be less than to be considered valid. A lower target means fewer valid hashes exist, making it harder to find one. The target is derived from the difficulty value using a formula that maps difficulty 1 to a specific maximum target. When difficulty doubles, the target halves, meaning miners need twice as many hash attempts on average.

Question 2

How often does Bitcoin difficulty change?

Accepted Answer

Bitcoin's difficulty adjusts every 2,016 blocks, which takes approximately two weeks at the 10-minute target block time. The adjustment factor is capped at 4x in either direction to prevent extreme swings. Other proof-of-work chains use different adjustment schedules — for example, Ethereum Classic adjusts every block using an exponential moving average.

Question 3

What are leading zeros in a block hash?

Accepted Answer

Leading zeros refer to the zero digits at the beginning of a block hash when represented in hexadecimal. More leading zeros mean the hash is a smaller number, which corresponds to a higher difficulty. At Bitcoin's current difficulty, a valid block hash requires approximately 19 leading hexadecimal zeros. This visual pattern makes it easy to see how difficulty affects the search space.

Difficulty Challenge

Difficulty Challenge