Chainlink is a decentralized blockchain oracle network. Chainlink's token is on Ethereum. The network is intended to be used to facilitate the transfer of tamper-proof data from off-chain sources to on-chain smart contracts.

Chainlink was created in 2017 by Sergey Nazarov and Steve Ellis, who co-authored a white paper introducing the Chainlink protocol and network with Cornell University professor Ari Juels the same year. Chainlink acts as a "bridge" between a blockchain and off-chain environments. The network, which services smart contracts, was formally launched in 2019.

In 2018, Chainlink integrated Town Crier, a trusted execution environment-based blockchain oracle that Juels also worked on. Town Crier connects the Ethereum blockchain with web sources that use HTTPS.

In 2020, Chainlink integrated DECO, a Cornell project co-created by Juels. DECO is described by its authors as a protocol that uses zero-knowledge proofs to allow users to prove information is true to a blockchain oracle without revealing sensitive information, such as birth dates.

Chainlink's oracle network allows blockchains to connect to off-chain data and computation resources.

LINK is a utility and governance token of Chainlink. The trade value derived from these tokens is used to pay node operators for retrieving data from smart contracts, and also for deposits placed by node operators as required by contract creators. Tokens can be stored in any ERC-20 wallet, as the ERC677 token retains all the functionality of an ERC-20 token. Community participants can stake LINK to support the network's cryptoeconomic security.