A decentralised application (DApp, dApp, Dapp, or dapp) is an application that can operate autonomously, typically through the use of smart contracts, that run on a blockchain or other distributed ledger system. DApps provide a function or utility to their users with less human intervention. Control over some DApps is distributed over holders of tokens that represent ownership over a DApps governance. Without any one entity controlling the system, the application is therefore decentralised.

DApps are conventionally open-source. Some DApps that are fully closed-source and partially closed-source also exist. Bitcoin, the first cryptocurrency, is an example of a DApp.

DApps can be classified based on whether they operate on their own block chain, or whether they operate on the block chain of another DApp.

Smart contracts are programs that maintain data on a blockchain and execute operations. Multiple smart contracts can be developed for a single DApp to handle more complex operations. Over 75% of DApps are supported by a single smart contract, with the remainder using multiple smart contracts.

DApps incur fees paid to the validators of the blockchain, known as "gas", due to the cost of deploying and executing the DApp's smart contracts. The amount of gas required of a DApp's functions is dependent on the complexity of its smart contracts. A complex smart contract of a DApp that operates on the Ethereum blockchain may fail to be deployed if it costs too much gas, leading to lower throughput and longer wait times for execution.

DApps generally rely on the consensus mechanism of the blockchain or distributed ledger on which they run, rather than operating a separate consensus mechanism. Common blockchain consensus mechanisms include proof-of-work (PoW) and proof-of-stake (PoS).

In proof-of-work systems, miners expend computational work to validate blocks. In proof-of-stake systems, validators participate in block validation by staking assets.