What is a token swap
A token swap is a direct exchange of one digital asset for another within a blockchain using a smart contract. Unlike centralized exchanges and online exchangers, such an operation is carried out without the involvement of third parties — through the interface of a DEX platform or a non-custodial crypto wallet*.
* A non-custodial wallet is a software or hardware solution for storing and managing cryptocurrency in which the user independently controls the private keys. No third party — including wallet developers, exchanges, or services — has access to the funds or can dispose of them without the owner’s signature. This approach eliminates the risks of asset blocking, account freezing, or fund seizure typical of custodial services; however, it fully transfers responsibility for security, seed phrase storage, and the correctness of signed transactions to the crypto user.
Note. Initially, such operations were called atomic swaps and were based on the HTLC (hashed timelock contract)* mechanism. Over time, with the emergence of DEX exchanges and liquidity pools, the term “swap” began to be used in a broader sense, referring to a different exchange principle.
* HTLC (Hashed TimeLock Contract) is a type of smart contract used for atomic swaps that combines two key mechanisms: cryptographic condition verification and a time constraint on the transaction. Assets are locked in the contract and can only be claimed upon providing a predefined cryptographic hash. If the conditions are not met within the specified time window, the contract automatically cancels the transaction and returns the funds to the original owner. This model enables trustless exchanges between parties, eliminating the risk of unilateral refusal and asset loss.
Main types of token swaps
Atomic and intra-network swaps
The classic swap model involves exchanging tokens within a single blockchain. In practice, such operations are most often carried out through liquidity pools* on decentralised exchanges, including:
* A liquidity pool is a smart contract on a decentralized exchange that holds a specific ratio of two or more tokens provided by users. These assets enable instant exchanges without requiring a counterparty at the time of the transaction. Users who supply tokens to the pool become liquidity providers and receive rewards in the form of a share of the fees paid for swaps. The fee amount and yield depend directly on trading volume and the user’s share of the pool.
Most modern DEX platforms use the Automated Market Maker (AMM)* model, first introduced by Uniswap in 2020. However, there are also platforms that operate based on order books*, as well as hybrid solutions.
* AMM (Automated Market Maker) is an algorithmic trading mechanism used on decentralized exchanges in which asset prices are determined automatically based on a mathematical formula and the current token balance in a liquidity pool. Unlike traditional markets, AMMs do not require an order book or the active presence of buyers and sellers. Any user can perform a swap at any time, and changes in the pool’s asset balance automatically adjust prices, ensuring continuous liquidity.
* Order book — a traditional trading mechanism representing an ordered list of buy and sell orders for an asset, indicating price and volume. A trade occurs only when the price and volume of matching orders coincide. This approach provides more precise market pricing but requires high liquidity and the simultaneous presence of many participants. On decentralised platforms, this often leads to execution delays and liquidity gaps.
How swaps work in AMM protocols
The token exchange process in AMM systems looks as follows:
- The user selects a trading pair (for example, ETH/USDT) and initiates a swap via the DEX interface.
- The transaction is confirmed in the wallet, after which ETH tokens are sent to the liquidity pool.
- The smart contract automatically calculates the equivalent amount and sends USDT to the user’s wallet.
The entire process is fully automated and does not require intermediaries. The transaction fee is determined by the protocol’s rules.
Sometimes the asset price on a DEX may differ from the market price. In such cases, arbitrage* traders step in, earning from the price difference and thereby aligning the price.
* Cryptocurrency arbitrage is a trading strategy based on extracting profit from price discrepancies of the same asset across different markets or protocols. Arbitrage traders buy a token where it is temporarily cheaper and sell it where the price is higher. In addition to generating profit, arbitrage performs an important systemic function: it helps align prices between decentralised and centralised platforms, increasing the efficiency and stability of the crypto market.
Cross-chain swaps
In addition to swaps within a single network, there are cross-chain swaps — operations in which tokens are exchanged between different blockchains. For this purpose, specialised protocols and cross-chain bridges* are used, such as LayerZero.
* A cross-chain bridge is a specialized protocol that enables the transfer of digital assets and data between independent blockchains. Cross-chain bridges allow tokens to be used outside their native blockchain, facilitate cross-chain swaps, and enable interaction between ecosystems that are architecturally incompatible by design.
Example of a cross-chain swap:
- The user swaps ETH from the Ethereum network for USDT on the Polygon network.
- The smart contract for the cross-chain protocol has been activated.
- ETH is locked in a liquidity pool on the Ethereum network.
- An equivalent amount of USDT is sent to the user from a liquidity pool on the Polygon network.
Advantages and risks of token swaps
Advantages
The main advantage of swaps is decentralisation. Users do not depend on centralised exchanges that may restrict operations or block accounts.
Additional benefits:
- no mandatory verification or KYC;
- fast exchanges without deposits and withdrawals;
- no additional deposit fees;
- access to a wide range of tokens;
- ability to create liquidity pools independently;
- Reduced fraud risk due to automatic smart contract execution.
To enhance privacy, crypto mixers* are sometimes used, though they carry regulatory risks.
* Crypto mixers are specialized services designed to enhance the privacy of blockchain transactions by pooling funds from a large number of users and redistributing them to new addresses. As a result, it becomes difficult, if not impossible, to establish a direct link between the sender and the recipient of specific assets, significantly reducing transparency into transaction history. At the same time, crypto mixers often attract regulatory attention because they can be used not only to protect privacy but also to conceal the origin of illegally obtained funds. For this reason, such services frequently face legal restrictions, sanctions, or shutdowns, and engaging with them may increase users' future risks.
Note. As DeFi evolves, anonymous swaps may become less accessible. Some major DEX platforms are already implementing elements of KYC* and AML*.
* KYC (Know Your Customer) is a set of user verification procedures applied by financial and cryptocurrency platforms to confirm a client’s identity. KYC typically involves collecting personal data, document verification, and, in some cases, biometric verification. Implementing KYC aims to reduce fraud, money laundering, and illicit financing risks, but it also limits user anonymity and reduces privacy when using decentralised services.
* AML (Anti-Money Laundering) is a set of regulatory requirements, technical measures, and procedures aimed at detecting, preventing, and suppressing money laundering and the financing of illegal activities. In the cryptocurrency environment, AML mechanisms may include transaction monitoring, source-of-funds analysis, blocking suspicious addresses, and cooperation with regulators.
Risks
The main threats associated with swaps are security-related:
- vulnerabilities or hacks of smart contracts;
- phishing* attacks and fake interfaces;
- signing approvals for malicious contracts.
* Phishing is a form of fraud in which attackers create fake websites, interfaces, or smart contracts that visually mimic legitimate platforms. The goal of phishing is to deceive users and gain access to their wallets or token management permissions. Once a malicious transaction or approval is signed, attackers can freely withdraw funds, and such actions cannot be reversed on the blockchain.
An additional risk is low liquidity in certain trading pairs, which leads to slippage*.
* Slippage is the deviation of the actual exchange rate from the expected price shown to the user when initiating a swap. On decentralised exchanges, it occurs due to changes in the asset balance in the liquidity pool during trade execution. The lower the liquidity of a trading pair and the larger the swap volume, the greater the price impact and the higher the likelihood of significant slippage, especially during periods of high crypto market volatility.
Difficulties may also arise for beginner users who are unfamiliar with how DEX platforms and crypto wallets work.