Smart contracts move money, enforce deals, and automate financial systems without human involvement. They’re reshaping how organizations think about liquidity, execution, and control, but getting them right requires understanding how they run.

Below, we’ll explain how smart contracts operate, what powers them, and how to deploy them safely.

What’s in this article?

• What are smart contracts?
  
• How does a smart contract appear on blockchains?
  
• How do smart contracts automate transactions?
  
• What risks affect smart contracts?
  
• How can organizations deploy smart contracts safely?
  
• How Stripe Payments can help
  

What are smart contracts?

Smart contracts are self-executing programs stored on blockchains. They run when specific conditions are met, so there are no lawyers, no intermediaries, and no manual steps. They rely on oracles, which are trusted data feeds that provide information. Oracles unlock use cases such as flight insurance that pays automatically if your flight is delayed, escrow that releases only if a verified delivery is made, and market protocols that adjust based on real-time prices.

Once a smart contract is deployed, it can’t be changed. It executes exactly as written, and everyone on the network can verify the result. It’s automation that doesn’t rely on trusting other people.

How does a smart contract appear on blockchains?

To publish a smart contract, users write a contract, compile it into bytecode (the low-level instructions that the network understands), and deploy it onto the blockchain.

Once a smart contract is published to a blockchain, it has its own address. If it’s a public smart contract, anyone can send it data or payments, and it will run exactly as programmed. There’s no central server and no admin panel.

When someone interacts with a smart contract, their transaction is also sent to the blockchain. Every full node on the network picks up the transaction, runs the contract’s logic locally, and verifies the outcome. If the code completes successfully, the new state (e.g., balances or records) is written to the chain. If it fails, the transaction reverts to the original state.

How do smart contracts automate transactions?

Smart contracts hold assets such as tokens or stablecoins, monitor for specific events or inputs, and then execute preprogrammed outcomes when conditions are met.

Here are some examples:

• Supply chains: A shipping sensor signals delivery confirmation, and a smart contract releases payment to the supplier.

• Decentralized finance (DeFi) lending: Users deposit collateral, and the smart contract calculates interest, issues loans, handles repayments, and liquidates risk.

• Nonfungible tokens (NFTs) and royalties: A digital artwork gets resold, and the smart contract sends the original creator an automatic royalty.

• Payouts and subscriptions: Smart contracts power recurring stablecoin subscriptions and international payouts. Contracts run the schedule and settle payments nearly instantly.

What risks affect smart contracts?

Once deployed, a smart contract’s code is usually immutable. And because smart contracts are software, they can have bugs that move money to the wrong place. In the first half of 2025, attackers stole over $2.17 billion from crypto protocols, including through contract exploits.

Other potential weak points:

• Unreliable underlying data: Smart contracts rely on oracles. If the oracle reports a wrong price or a fake delivery confirmation, the contract will still act on it.

• Control keys: Admin controls or upgrade keys can also be weak points. If a private key is phished (i.e., attained through fraud) or stolen, the attacker can use the smart contract for their own gain. Some teams use multisignature wallets or time locks to reduce this risk, but these features aren’t always implemented.

• Poor incentive design: Flash loan attacks, sandwich trading, or the manipulation of poorly defended contracts can drain funds without raising alarms. The contract might behave exactly as coded and still be breached.

How can organizations deploy smart contracts safely?

You get only one chance at deploying a smart contract.
Here’s how to do it successfully:

Audit the code

Every contract should go through a full security audit, ideally by an independent firm with deep blockchain expertise. Auditors look for re-entrancy flaws, faulty permission logic, and edge cases that drain funds or lock them permanently. Good audits will test assumptions, simulate attacks, and suggest defensive improvements.

Test every path

Use frameworks to simulate transactions, failures, and unusual cases. That includes forking mainnet data to test against real-world conditions; simulating malicious inputs, race conditions, and failures; and covering unhappy paths just as thoroughly as ideal flows.

Use hardened components

Smart contracts usually don’t need to be built from scratch. Use audited templates for tokens, access control, and math. Stick to well-established standards (e.g., ERC-20 for fungible tokens or ERC-721 for nonfungible tokens) and reuse what’s been battle-tested, unless you have a very good reason not to.

Deploy gradually

Start with limited funds or user access. Let the smart contract run in production with constraints before scaling. Some teams even integrate circuit breakers, such as transaction caps or pause switches, in case something goes wrong. Use multisignature wallets and time locks to manage those controls responsibly. Then, if the contract is mature, consider renouncing control entirely.

Watch everything

Live contracts can be monitored, so track unusual activity, transaction spikes, or failed interactions. Build alerts. If you do have emergency controls, be ready to use them fast when needed.

How Stripe Payments can help

Stripe Payments provides a unified, global payments solution that helps any business – from scaling startups to global enterprises – accept payments online, in person and around the world. Businesses can accept stablecoin payments from almost anywhere in the world that settle as fiat in their Stripe balance.

Stripe Payments can help you:

• Optimise your checkout experience: Create a frictionless customer experience and save thousands of engineering hours with prebuilt payment UIs, access to 125+ payment methods, including stablecoins and crypto.

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• Unify payments in person and online: Build a unified commerce experience across online and in-person channels to personalise interactions, reward loyalty and grow revenue.

• Improve payments performance: Increase revenue with a range of customisable, easy-to-configure payment tools, including no-code fraud protection and advanced capabilities to improve authorisation rates.

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Learn more about how Stripe Payments can power your online and in-person payments or get started today.