How does the target work?
A block hash is a 256-bit number that looks random. The target is a line: any hash at or below it wins, and anything above it is thrown away. Written in hexadecimal, a low target starts with a long run of zeros, which is why people say a winning hash “starts with zeros”.
The header doesn’t store all 256 bits. It packs the target into a 4-byte field called bits, and every node unpacks it the same way.
How is the target set?
Every 2,016 blocks, each node compares how long those blocks took with two weeks. If they came faster, the target goes down, and if slower, it goes up, by at most four times either way. That keeps blocks about ten minutes apart as miners come and go.
Difficulty is the same thing on a friendlier scale: the easiest allowed target divided by today’s. The target falls as difficulty rises.
How many hashes does today’s target take?
That’s the average number of tries the whole network needs per block. Pools use the same idea with a much easier target of their own, so every machine sends back shares often enough to count its work.
Sources
- Target · Bitcoin Wiki
- Difficulty · Bitcoin Wiki
- Block chain guide · Bitcoin developer documentation
Live figures on this page come from the CloudMineCrypto API and public chain data, refreshed regularly, and are labelled where they appear. Educational only, not financial advice.