# Proof of Believability

IOST introduced Servi as both a measurement of users’ contribution to the community and a way to encourage members to contribute to the continued development of the IOSChain.

#### Used in

* IOST

  **Read more**
* [whitepaper](https://github.com/iost-official/Documents/blob/master/Technical_White_Paper/EN/Tech_white_paper_EN.md#consensus-mechanism)