Transaction is expected to fail

While swapping on the Uniswap Wallet this error may appear.

 

 

This error is meant to prevent the swapper from paying the network cost for a failed swap.

 

There are a few different reasons why this error may appear:

  1. A variable token buy or sell fee. Variable means the token fee can change.

    To determine your tokens fee see our article “How to find a token's fee”.

    The slippage of the swap needs to be higher than the tokens fee. If the token fee increases then you will have to manually increase your swaps slippage.

    To learn how to change a swaps slippage see our article “How to change slippage in the Uniswap Wallet”.

    For example: If the token has a sell fee of 10% then try setting the slippage to 11%, 12%, 13% or 14%.

  1. The token may be unsellable. Malicious token creators can add code to the token contract preventing anyone but themselves from swapping.

    To learn more about this see our article “Unsellable token scams”.

  1. A non standard approval function. Some tokens have a different approval process than most other tokens.

    Try revoking existing approvals for this token on Uniswap. Then try the swap again. To learn how to revoke token approvals see our article “How to revoke a token approval”.

    If you do not have any existing approvals then this may not apply to you.

  1. The token is causing a mathematical error. Rebase tokens and fee on transfer tokens have internal math which changes the swaps output. This extra math may interfere with the calculations of the swap.

    Try swapping for even/exact outputs or inputs. Additionally, try playing with the input or output amount.

    For example: Swapping 10,000 tokens (an even amount) or for 0.3 ETH (an exact amount).

 

If you are seeing this error and none of these steps help then please reach out to the Uniswap support team.

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