what is the nonce 
nonce a portmanteau of number used only once is a number that the bitcoin mining program uses it is included in the block header then that information is hashed if the resulting hexadecimal number adds up to a value of less than or equal to the network s difficulty target the miner s block is added to the blockchain another is opened and the process begins again understanding the noncea bitcoin nonce is a 32 bit or 4 byte number miners use to attempt to generate a valid hash to produce a new block in the bitcoin blockchain the nonce is one of the fields included in the block header which also includes on the bitcoin network participants called miners compete to generate a hash that is less than or equal to the network target hash by repeatedly changing the nonce after each unsuccessful attempt hashing refers to the process of applying a cryptographic hash function to information the cryptographic hash function is a mathematical operation that takes block data and encrypts it by transforming it into a unique value a fixed length output of hexadecimal characters this hash value serves as a cryptographic fingerprint of the block ensuring that the block s contents remain unaltered the nonce is the only variable in the block header that a miner can modify by changing the nonce a miner can change the hash of the block and calculate different possible solutions for example this is the previous paragraph sent through an sha 256 hashing algorithm acd691b23cc47b03addf7329b0467c6190e758ee763d7d648af75b5c5ae73e3aby adding a value of zero the nonce at the end of the paragraph you get a different hexadecimal value if you change that zero to a one you d get this this is how the nonce is used by the bitcoin mining programming the nonce value is increased by one with every attempt until a certain value is reached the first miner to find a valid hash under the network s difficulty target is awarded the block reward their block is broadcast to the network added to the blockchain and the process begins again the target difficulty is a measure of how difficult it is to find a valid nonce it is adjusted periodically to maintain a consistent block generation rate extra nonce and time stampyou ll find in a block explorer that nonces generally only go up into the billions for example the nonce for block 841 948 was 1 614 498 317 block 841 949 had a nonce of 4 218 083 700 a modern mining rig can generate many more hashes than this in less than one second 12additionally the nonce is limited to 32 bits 4 bytes so it can only go up to a little more than 4 29 billion it has to roll over to be useful because hashing is so fast so an addtional method was created after bitcoin asic miners began ripping through the blockchain another number called the extra nonce is randomly generated and used in the coinbase data field this value is added to the coinbase transaction space which changes the merkle root the merkle root is part of the block header so the block header hash changes the extra nonce and the nonce are both manipulated to try to find the solution if a solution cannot be found using either of these the mining program allows the miners to adjust the timestamp the combination of these three values allows the blockchain to keep its target of mining one block about every 10 minutes 3