Nonce is an abbreviation of number used once.


The nonce is a field in the block header.

I call it "the mining field".

What's it used for?

Miners adjust the nonce when they're trying to get the hash of their block headers below the target. (i.e. Get a valid Block Hash for their candidate block.)

All of the other fields in the block header are predetermined, so the nonce is what allows you to create different hash results. Block 404,104


Why is it called a "nonce"?

Just one of those terms used in cryptography, like Alice, Bob, and whatnot.

In cryptography, a nonce is an arbitrary number that may only be used once.

I know, I prefer "the mining field" too.


By Greg Walker,

Last Updated: Mar 14 2018
  • Mar 14 2018: Renamed block-id to block-hash, finally
  • Nov 01 2017: glossary/nonce - added definition... 'number used once'
  • Feb 28 2017: - added xlinks
  • Jan 20 2017: - Rewrote, because target adjusts by itself, not from an internal difficulty value. Also added a handy svg diagram.
  • Jan 13 2017: tidied up glossary pages - css, formatting, restructuring
  • Jan 01 2017: Moved /manual/guide/ and /manual/reference/ to /guide/ and /glossary/