An airdrop is a distribution mechanic for cryptoassets, typically involving allocating free tokens to a wide user base. Allocations are often based on holdings of other cryptoassets or interaction with a project or service. Airdrops aim to leverage the network effects of existing projects to drive user engagement. Airdrops do not require users to contribute capital, and function partially as a marketing strategy to spread awareness. Notable examples include the Stellar airdrop to users of their web wallet and Ontology's airdrop to NEO token holders.