The easiest way to understand what dApps are is to compare them with apps you already use. A regular app keeps your money and data on the company's servers, while a decentralized app runs on a blockchain and follows code that nobody can quietly change. In this lesson, we'll break down what a dApp is made of, what happens after you tap a button, what kinds of dApps are out there and where the risks are hiding.
- A dApp is an app whose logic and funds live in smart contracts on a blockchain, not on a company's server.
- Instead of a username and password, you connect a crypto wallet and sign every action.
- Actions that change data on the blockchain cost a network fee, and a sent transaction can't be canceled.
- The main risks are bugs in contract code, lookalike phishing sites and dangerous token spending approvals.
How a decentralized app works
Let's use a banking app as an example. It has a screen with buttons, and behind that screen is the bank's server, which holds your money and the rules: which transfers are allowed and how much they cost. The bank can change those rules, freeze your account or simply shut the server down for the night.
A dApp works differently. Instead of a server, it has smart contracts: programs stored on the blockchain. They hold the funds and the rules, and thousands of network nodes run them at the same time. There's no single switch that can shut a program like that down, and its code is usually open, so anyone can check exactly what it does.
The screen you see in your browser, on the other hand, is usually a perfectly ordinary website on regular hosting. It can be blocked or faked. But even if the site disappears, the contracts keep running, and you can still reach them through a different interface.
So there's a kind of division of labor: the blockchain takes care of storage and integrity, the smart contracts handle the rules, the interface makes things convenient, and the wallet makes sure nothing happens without your consent. The weak link here is usually not the code but a person rushing to confirm a transaction.
- Interface: a website or mobile app with buttons.
- Smart contracts: code on the blockchain that holds funds and enforces the rules.
- User wallet: your way into the app and your tool for signing actions.
- Blockchain: the shared database where all transactions and balances are recorded.
Short for decentralized application. Pronounced "dap" or "dee-app". The key sign: the app's logic and users' funds sit in smart contracts, not under the control of a single company.
What happens when you tap a button
With a regular service, you sign up with an email and a password. A dApp has no sign-up: you tap Connect Wallet, and the app can see your address and balances. Nobody gives you a password, because the only thing that gets you access to your funds is the key in your wallet.
From then on, any action that changes data on the blockchain becomes a transaction, whether you're swapping tokens, depositing into a lending service or buying an NFT. You confirm each of these in your wallet and pay a network fee for it. Just looking at prices and balances is usually free.
Once you confirm, the transaction goes out to the network and lands in a block within a few seconds or minutes. From that point on, it can't be canceled, and there's no support team that will give you your money back. That's why dApps come with one simple rule: read what you sign.
Let's walk through an example. You want to swap 100 USDC for ETH on a decentralized exchange. First, your wallet asks you to allow the exchange's contract to spend your USDC. That's the first transaction, and it costs a small fee. Then you confirm the swap itself, which is the second transaction. A few seconds later, the ETH shows up in your wallet, and the blockchain keeps a record that anyone can look up.
- Open the app's website and check the address in the browser bar.
- Connect your wallet, for example MetaMask or Phantom.
- Choose an action: swap, deposit, buy.
- Your wallet shows the transaction details and the fee.
- You sign the transaction, and it goes out to the blockchain.
Before you swap a token for the first time, an app will often ask for permission to spend it on your behalf. Sometimes that permission has no limit. If the contract turns out to be malicious, it can take every one of those tokens, so it's a good idea to revoke old approvals from time to time.
Types of dApps
Most dApps are in finance, and this area is called DeFi. Decentralized exchanges like Uniswap let you swap one token for another with no sign-up and no middlemen. Lending protocols like Aave let you borrow crypto using other crypto as collateral, and the interest is calculated by code.
But there's plenty more: NFT marketplaces, games where the items belong to the player, prediction markets like Polymarket, and naming services like ENS that replace a long wallet address with a short name. Telegram hosts mini apps built on the TON blockchain, so lots of people use dApps without ever having heard the word.
dApps run on many different networks. Ethereum and its layer-2 networks have the biggest ecosystem, and there are plenty of apps on Solana, BNB Chain and TON. The network decides which wallet you need and how much each transaction costs.
It's easy to tell a dApp from a regular website: it asks you to connect a wallet, not enter your email. If a service asks you to send money to its address and promises to take care of everything, it's not a decentralized app anymore. It's a middleman you're trusting with your funds, just like any ordinary company.
dApps vs regular apps: a comparison
dApps have real strengths: nobody can freeze your account on a whim, the rules are visible to everyone, and you can use them from any country without opening an account. But you pay for that freedom with responsibility and convenience.
Forget your banking password, and the bank will reset it once you prove who you are. Lose your wallet's recovery phrase, and you lose access to your funds in a dApp for good. The table below sums up the main differences.
At the same time, the line between the two worlds is blurring. Many regular apps already have wallets and blockchain built in, and users may not even notice they're signing transactions. The more familiar an interface looks, the more carefully you should check where your money is actually going.
| Regular app | dApp | |
|---|---|---|
| Login | Username and password | Connecting a wallet |
| Where funds are held | In the company's accounts | In smart contracts and your wallet |
| Who can change the rules | The company, at any time | Only as built into the contract |
| Reversing a mistaken transaction | Through support | Usually impossible |
| Cost of actions | Usually free for the user | A network fee for every transaction |
| Availability | Depends on the company and the country | Contracts run as long as the blockchain runs |
Risks and how to start safely
A smart contract's code can't just be patched after launch, so a bug turns into a hole hackers can use to drain funds. An audit lowers that risk but doesn't eliminate it: even audited protocols have been hacked. The second common risk is lookalike sites that copy a popular dApp's interface and ask you to sign a transaction that hands your tokens over to scammers.
Decentralization also comes in degrees. The team often keeps admin keys that let it change contract settings, and the interface runs on an ordinary server. Before you deposit any meaningful amount, find out who controls the protocol and how long it has been running.
A few simple habits take care of most of the risks. Open apps from a bookmark, not from links in ads or direct messages. If your wallet shows a transaction you don't understand or a signature request with no explanation, reject it: a legitimate service won't hold it against you. Every few months, review the approvals you've granted with a dedicated revoke tool and remove the ones you no longer need.
Start with a separate wallet and small amounts. We'll cover choosing and setting up a wallet in the lesson on Ledger, Trezor and MetaMask wallets, and you'll find a detailed look at how contracts operate in the lesson on how smart contracts work.
Set up a separate wallet just for trying new dApps and keep only a small amount in it. Keep your main savings at a different address that you never connect to unfamiliar sites.
Without connecting a wallet, open the Uniswap interface (type app.uniswap.org in by hand rather than clicking an ad) and enter a swap of 100 USDC for ETH. Note how much ETH the interface quotes and what network fee it estimates, then switch the network to Arbitrum or Base and compare. You'll see that the same dApp costs different amounts on different networks, and that you don't need a wallet at all just to check prices.
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FAQ
Do I have to pay to use a dApp?
Viewing data is usually free, but the network charges a fee for every action that changes the state of the blockchain. On Ethereum, that fee can be noticeable, while on Solana, TON and layer-2 networks it's usually pennies. Some apps also charge their own fee, for example on swaps.
Can a dApp steal my money?
An app can't move your funds without your signature. The real danger is different: you might sign a malicious transaction or give a contract an approval that's far too broad. So before you confirm anything, check the site's address and read what your wallet is showing you.
What's the difference between a dApp and a smart contract?
A smart contract is a program on the blockchain. A dApp is a complete app: one or more contracts, an interface for people and a connection to your wallet. Think of the contract as the engine and the dApp as the whole car.
Can I use dApps on my phone?
Yes. Many mobile wallets have a built-in dApp browser, and Telegram runs mini apps on TON. The same safety rules apply: check the address and the details of every transaction.
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