curve.fi
Curve.fi Slippage Settings and Swap Completion
Curve.fi slippage settings determine how far swap output may fall below the quote before the transaction rejects the exchange. A tighter tolerance raises the minimum acceptable output, increasing the chance of rejection when pool conditions change. A wider tolerance permits a lower return and can accommodate more movement before execution. Neither setting improves the underlying quote or guarantees completion. The useful comparison starts with the same input amount, output token, and route. It then separates the price already available from the additional deterioration you would accept. Transaction status and the tokens actually received establish whether the submitted exchange completed.
Tighter output protection versus more execution room
Choosing between tighter and wider tolerance means comparing the minimum tokens each setting permits against the same quote. Changing the percentage changes that boundary; it does not add liquidity or reserve a price.
A tighter tolerance
A smaller percentage keeps the minimum closer to the expected output. This fits a decision to reject the exchange when even modest deterioration makes it unacceptable. Pool balances can change between quoting and execution, so an otherwise valid swap may revert. Rejection preserves the swap principal, but an included transaction still incurs gas costs for the work the network performs.
A wider tolerance
A larger percentage permits more adverse movement before the output check fails. That can help a swap complete during changing conditions, provided its other requirements hold. It also authorizes a worse exchange. Compare the resulting minimum amount with the amount you actually need, rather than treating a successful transaction as sufficient evidence of an acceptable trade.
What does the minimum received amount protect?
The minimum received amount protects the output quantity specified in the swap transaction, using the selected token and its smallest transferable units. For a fixed input quote, the basic relationship is minimum output = quoted output × (1 − tolerance), with tolerance expressed as a decimal fraction. Token precision determines the final representable amount. The percentage is a way to prepare the transaction; the contract evaluates its encoded minimum.
That boundary applies to the quote used when preparing the swap. A later quote can produce a different minimum with the same percentage. Refreshing the screen also does not rewrite a transaction already signed. Keeping the original quote and submitted minimum distinguishes a changed market from a changed instruction.
Price impact already inside the quote
Price impact reflects how the proposed trade changes its exchange rate through the available liquidity, while tolerance allows additional deterioration relative to the quote. A large trade against limited output liquidity can begin with an unattractive quote even before any waiting occurs. Pool balances, the pricing mechanism, and trading fees contribute to that output. Tightening tolerance cannot remove a cost already present in the quoted exchange. The displayed price impact and the minimum received therefore answer different questions: whether the proposed trade already moves the price substantially, and how much worse execution may become.
Can changing the swap amount help it complete?
Reducing the swap amount can lessen its effect on pool balances, but the new amount needs a fresh quote and still faces changing conditions before execution. Compare the output per input token and the displayed price impact. A smaller exchange completes less of the intended trade, so its lower total output alone says nothing about the quality of its rate.
Route choice also changes the comparison. Curve’s routing software searches available paths before the router executes the chosen route, while a direct pool swap uses the selected pool. Where both support the intended exchange, keep the input amount, token pair, network, and tolerance the same, then compare each path’s quoted output, minimum output, and estimated network cost. A direct path may require less gas, but it does not automatically provide a better price or stronger slippage protection. Neither path guarantees execution after the quote.
A rejected swap followed by a fresh quote
Consider a hypothetical swap with enough input tokens, sufficient spending allowance, and funds for gas. All amounts, percentages, and execution outcomes in this example are illustrative, not live settings. The quote returns 1037 output tokens. A 0.2% tolerance gives a minimum of 1034.926 tokens; a 0.6% tolerance gives 1030.778. Assume the selected token supports these decimal amounts. With unchanged conditions, the quoted output clears either minimum.
The reader submits the tighter option, but another trade changes the pool before execution. The exchange would now return 1032.4 tokens. That falls below 1034.926, so the swap reverts. The same output would clear the wider option’s minimum, assuming every other execution condition held. The reader confirms the failed transaction before considering another attempt; the original swap has not delivered output tokens.
For recovery, the reader keeps the tighter tolerance and obtains a fresh quote of 1038 tokens. Its new minimum is 1035.924. After reviewing that amount, the reader submits a new transaction, which succeeds and delivers 1036.2 tokens. The receipt and corresponding token transfer confirm completion above the submitted minimum. The rule stayed the same; the quote and resulting threshold changed. If the fresh minimum had become unacceptable, this recovery would stop before another submission.
Why can a swap fail even with wider tolerance?
A swap can fail despite wider tolerance because token authorization, available balances, contract execution, and network processing impose requirements separate from the output minimum. Increasing tolerance addresses only an output shortfall relative to that minimum.
Failures before submission
A rejected wallet request or failed transaction simulation can prevent submission altogether. Missing allowance, insufficient input tokens, or inadequate gas funds require their own correction. An interface error alone does not establish whether anything reached the network. A transaction hash provides a record to investigate, but does not prove successful execution. Diagnose that state before changing a price setting.
Reverts after inclusion
The Curve router reverts an exchange when its final output falls below the submitted minimum. Other contract checks can also reject execution, and an insufficient gas limit can cause failure. The failed transaction’s status and available error details help distinguish those causes. Repeating an identical failing call can incur another network fee without resolving its underlying problem.
Pending transactions and the final token receipt
A pending transaction has no successful execution receipt yet. Closing the interface, changing its tolerance, or requesting another quote does not cancel the signed transaction. Starting a separate swap while the first remains unresolved can create another valid exchange, rather than repair the first. Wallet replacement or cancellation features have their own network conditions and only take effect if the replacement wins inclusion.
A successful receipt establishes execution; its token transfers identify the output delivered to the receiving address. Compare that amount with the submitted minimum, using matching token units. A wallet’s total balance can also include unrelated transfers, so the transaction record supplies the more precise comparison. Further action depends on whether the original transaction succeeded, reverted, or remains pending.
Details worth knowing about Curve.fi
Can a Curve.fi swap return more tokens than the quote?
A swap can return more tokens than its quote if execution conditions improve before it runs. The minimum-output check sets a floor, rather than a cap. Favorable pool changes can therefore increase the amount received, although the quote does not promise that improvement.
Does slippage tolerance protect the cash value of the tokens I receive?
Slippage tolerance protects a token quantity relative to the swap quote, not its cash value after receipt. The output token can change in market value while the transaction still meets its minimum. A displayed currency estimate and the contract’s output threshold measure different things.
How does token rounding affect a very tight slippage setting?
Token precision limits the minimum amount a transaction can represent. A percentage calculation may produce more decimal places than the output token supports, requiring conversion into whole smallest units. Small rounding differences matter more when the permitted gap between the quote and minimum is extremely narrow.
Is zero slippage tolerance the same as zero trading cost?
Zero tolerance does not remove trading fees, price impact, or network charges; where the interface permits it, it leaves no intended allowance for adverse output movement beyond the prepared quote, subject to token precision.
What protection does tight tolerance provide against sandwich attacks?
Tight tolerance reduces the adverse output movement an attacker can impose while keeping the swap executable. A sandwich attack places trades around a victim’s exchange to profit from the resulting price movement. The minimum limits acceptable output deterioration, but it does not conceal a public transaction or eliminate every profitable ordering strategy.