crypto swaps

A crypto swap is a single operation that changes which asset you hold: token A goes in, token B comes out, priced at the market rate available on whatever liquidity the route touches. A transfer moves the same asset to another address — a swap changes the asset itself. A bridge moves value between networks — a same-chain swap never leaves its chain.

Custody separates a wallet-based swap from a centralized exchange: on a centralized exchange you deposit funds and the venue holds them while you trade, while in a non-custodial swap your wallet authorizes the execution and receives the output directly; the contracts handle settlement in between. Non-custodial describes who holds the keys. If you're new to the mechanics, Ethereum.org's token-swapping walkthrough covers the basic flow.

A crypto swap defines the pair and amount, finds an executable route, shows the output floor, collects approvals and signatures, then settles on-chain:

1. Define the trade. Source chain, destination chain, input token, output token, amount.
2. Routing. A router queries liquidity pools, open orders, or market makers and calculates one or more executable routes — aggregator APIs such as the 0x API exist precisely to solve this search problem.
3. Review the quote. Expected output, price impact, slippage tolerance, network cost, provider fees, and the minimum received figure. The minimum received is your real floor — read it.
4. Approve, then sign. For most ERC-20 tokens you first sign an allowance transaction letting the swap contract spend your input token, then sign the swap itself.
5. Settlement. Same-chain swaps complete in one transaction, gated only by network confirmation. Cross-chain routes chain a source swap, a bridge or solver transfer, and a destination swap — so completion also depends on source finality, message passing, and execution on the far side.

Networks are identified by numeric chain IDs — Ethereum Mainnet is 1, Polygon 137, Arbitrum One 42161, Base 8453 — often written in CAIP-2 form as eip155:1, eip155:137, and so on; the CAIP-2 specification defines that chain-reference format.

Swap types differ by where the price is formed and how many execution systems the route uses:

• AMM swaps. You trade against a liquidity pool priced by a formula, as implemented in open-source contracts like Uniswap v4 core; an automated market maker is the general model. Price impact grows fast when your trade is large relative to pool liquidity.
• Order-book / RFQ trades. A market maker quotes you a firm price off-chain and fills it on-chain. Better for size; you're trusting the quoted route instead of a curve.
• DEX aggregation. A router splits your order across multiple pools and venues to improve the effective rate. You inherit the risk of every contract in the path.
• Solver-based swaps. You express intent; competing solvers find execution. Convenient, but read what you're actually signing.
• Cross-chain swaps. Asset in on one chain, different asset out on another, via bridge or solver infrastructure — THORChain's docs describe one native-asset approach. This is the highest-complexity category: more steps, more finality assumptions, more failure points.
• Peer-to-peer atomic swaps. Two parties exchange directly via contracts that settle both legs or neither. Trust-minimized but rarely the practical choice for routine trades.

The amount that lands in your wallet is the input trade less liquidity, protocol, network, bridge, price-impact, and slippage costs. Total cost is a stack of separate components:

• Liquidity-provider fees taken by the pool or venue that fills your trade.
• Protocol or integrator fees charged by the interface or router you used.
• Network gas for the approval and the swap transaction — and on cross-chain routes, gas on both chains.
• Bridge or messaging costs if the route crosses networks.
• Price impact — the movement your own trade causes against the pool, which rises sharply when trade size is large relative to available liquidity.
• slippage in finance — price movement between quote and execution. Your slippage tolerance sets how much you'll accept; the minimum received field encodes that floor.

Compare minimum received, not the headline rate: a quoted rate can look better while gas and price impact make the amount delivered lower. Public dashboards such as DefiLlama's DEX data let you compare venue-level activity when checking whether a pool is deep enough for your size.

Swaps are as safe as the weakest link in the route — the contracts, the token, the bridge, and the interface you're sitting in front of. Audited and open-source code reduces certain risks; it does not eliminate them. Non-custodial changes who holds the keys, not the contract, token, bridge, or interface risk.

The risk list is specific: smart-contract bugs in the pool or router; malicious or worthless tokens (anyone can deploy a token with a familiar name); unlimited or lingering approvals that leave a spender authorized to move your tokens later; cross-chain routes that depend on bridge and messaging security on top of everything else; and phishing interfaces that mimic a legitimate swap UI to harvest signatures.

Before signing, verify the domain, confirm the chain ID matches your intended network, check the token contract address against a known source rather than the ticker, and read the approval spender and amount. Approve what the trade needs rather than unlimited where you can, and never sign a transaction your wallet renders as unreadable or unexpected.

To do a crypto swap, connect the wallet, choose assets and amount, inspect the quote, set slippage, approve, sign, and confirm arrival:

1. Connect your wallet and confirm you're on the right network — check the chain, not just the logo.
2. Select the input token, output token, and amount. Verify the output token by contract address if it's anything obscure.
3. Read the quote: expected output, price impact, network cost, any provider fee, and minimum received. If price impact looks heavy, reduce size or split the trade.
4. Set slippage tolerance deliberately — tight enough to protect you, loose enough that normal volatility doesn't revert the transaction.
5. Sign the approval transaction if prompted, reviewing the spender and amount.
6. Sign the swap. For cross-chain routes, keep the tab open and track each leg; settlement takes longer than a single-chain swap and depends on finality on both sides.
7. Confirm the output token actually arrived in your wallet on the destination chain before calling it done.

Swap failures are usually identifiable from the wallet status and quote fields, so match the symptom to its cause:

• Transaction reverted. Usually slippage: the price moved past your tolerance between quote and execution. Raise the tolerance slightly or trade smaller. Also check you had enough of the native token for gas.
• Stuck pending. The gas price you set is below what the network currently wants. Speed it up or cancel from your wallet — don't resubmit blindly.
• Approval succeeded, swap didn't. The allowance is a separate transaction; nothing is broken. Just sign the swap itself.
• Swap done but no tokens visible. Often a display issue — add the token contract to your wallet's asset list. Verify on a block explorer before assuming the worst.
• Cross-chain route stalled. The source leg confirmed but the destination hasn't executed. Check the route's status tracker; these routes settle on the far chain's schedule, not yours.
• Output far below the quote. You were sandwiched or the route was thin. Next time: smaller size, tighter slippage, or a route with deeper liquidity.