What is slippage?

Slippage is the difference between the price or amount expected from a swap and its executed result. Market conditions can change after the quote appears, leaving the amount received below or above the expectation.

Are slippage and slippage tolerance the same thing?

Example

Slippage describes the realized difference; tolerance describes the acceptable boundary. In a hypothetical swap expected to return 100 tokens, receiving 99 represents 1% negative slippage measured by output amount. Receiving 101 is an equally sized positive difference. The example excludes fees and other deductions.

A 1% tolerance does not mean every trade loses 1%. Execution can fail if conditions cross the permitted boundary. Raising tolerance can allow a worse result; the setting does not produce a better price by itself.

Why is slippage not a transaction fee?

Slippage is a difference in the outcome, not a fixed payment to a service provider. Gas fees pay for network execution. The effect of your own trade on pool pricing is considered price impact. Treating every percentage on a swap screen as one fee mixes separate concepts.