A DApp is short for decentralised application. The definition is: a program whose backend logic lives in smart contracts on a blockchain rather than on a company’s servers. The frontend — the bit you see in a browser or an app — is usually a normal website, but when you click a button that moves money, the transaction goes to a smart contract and the state change happens on-chain, with no central operator in the middle.
That is the strict definition. The looser one, which is how the term is usually used, includes anything that connects to a wallet and interacts with a blockchain in any form. By that standard, every DeFi protocol interface, every NFT marketplace, every Web3 game, every on-chain social app is a DApp.
Why the Architecture Matters
The interesting thing about a DApp is not what it looks like but what cannot happen to it. Because the backend is a smart contract on a public blockchain, the following are all impossible in the way they are possible for a normal web app:
- The operator cannot freeze your account (they do not have an account of yours to freeze).
- The operator cannot change the rules retroactively (the contract’s bytecode is public and usually immutable after deployment).
- The operator cannot take the service offline (the contract keeps running whether the original team exists or not).
- There is no single server to hack (the state is distributed across every node in the network).
These properties are real and they are the reason DeFi works at the scale it does. Uniswap has processed trillions of dollars of trades. Aave has intermediated hundreds of billions of dollars of loans. None of it relies on the goodwill of the project teams who originally wrote the code, because the code does not need them in order to keep running.
The Caveats
The frontend is still centralised. The website you visit to use Uniswap is hosted by the Uniswap team, and they can and do block access to specific addresses or jurisdictions for regulatory reasons. You can usually still access the underlying contracts directly through other interfaces, but most users do not know how, so “the DApp is censorship resistant” is an asterisked claim in practice.
The upgradeability story is also messy. Many DApps use proxy patterns that let an admin key upgrade the implementation of a contract, which re-introduces a central point of failure. And the wallet you use to interact with a DApp is usually custodial or semi-custodial in some sense, so the end-to-end trust model is rarely as clean as the pitch suggests.
DApps are a real category of software that does real things a normal web app cannot. They are also not magic, and the gap between the architectural diagrams and the lived user experience is worth knowing about before you believe everything in the pitch deck.