Witnet is a decentralized oracle network (DON) that connects smart contracts to the outer world. Generally speaking, it allows any piece of software to retrieve the contents published at any web address at a certain point in time, with complete and verifiable proof of its integrity and without blindly trusting any third party. Witnet runs on a blockchain with a native protocol token (called Wit), which miners - called witnesses - earn by retrieving, attesting, and delivering web content for clients. On the other hand, clients spend Wit to pay witnesses for their Retrieve-Attest-Deliver (RAD) work. Witnesses also compete to mine blocks with considerable rewards, but Witnet mining power is proportional to their previous performance in terms of honesty and trustworthiness—this is, their reputation as witnesses. This creates a powerful incentive for witnesses to do their work honestly, protect their reputation, and not deceive the network.Witnet protocol builds upon a series of novel components:Decentralized Oracle Network (DON): We provide an abstraction for a network of independent providers to offer Retrieve-Attest-Deliver services. Later, we present the Witnet protocol as an incentivized, auditable and verifiable DON constructionReputation-Based Mining Protocol: We show how to construct a useful Proof-of-Work that can be used in consensus protocols. Miners do not need to spend wasteful computation to mine blocks, but instead must fulfill task assignmentsReputation-Based Task Assignment Protocol: We put forward an algorithm that is analogous to the Reputation-Based Mining Protocol and lets the network assign tasks to miners in a decentralized, fair, uniform, unpredictable yet deterministic wayBridge nodes: We describe a special kind of network participant that focuses on the ’Deliver’ part of the Retrieve-Attest-Deliver (RAD) tasks by allowing Witnet to interact with other blockchains.