Token swaps on Uniswap can fail for a variety of reasons. The most common causes for failed Uniswap transactions are slippage and insufficient funds. In this article, we will show you multiple tips that will help you understand why your Uniswap transaction is failing and what you can do to address the problem.
Key highlights:
- The "swap failed" error is one of the most commons errors encountered by users of the Uniswap decentralized exchange.
- The most likely cause for this error is that the swap that's being attempted would result in slippage exceeding the user's maximum slippage setting.
- The error could also be caused by your transaction taking too long to complete, or not having sufficient funds to pay the gas fee.
How to fix “swap failed” on Uniswap?
Here are the different reasons why transactions on Uniswap can fail and how you can fix them.
Your slippage tolerance settings are too low
Slippage is a common reason for a swap failed error. Slippage is a concept in trading which refers to the difference between the expected price of a trade and the actual price at which the trade is executed. The higher the slippage, the worse off you are.
When you’re making a swap on Uniswap, the interface provides a setting for the maximum amount of slippage you are willing to accept. If your trade is failing due to the slippage being too high, try making a smaller trade or adjust your slippage settings to allow more slippage. You should be careful when adjusting max slippage — consider making adjustments in small increments.
You can change your slippage settings by clicking the gearbox icon and selecting the “Custom” option under “Max slippage”. Then, you’ll be able to input the maximum amount of slippage you’re willing to accept.
Your transaction is taking too long to complete
If you initiated a token swap using the Uniswap interface, the swap might fail because the transaction is taking too long to complete. If the transaction takes more than 30 minutes, it will fail because the interface is designed to protect users from making a trade at a price that’s substantially different from the displayed price.
Usually, transactions should complete in a much shorter amount of time than 30 minutes, but they might take a very long time if your network fee limit settings are too low. If you’re determined to try and make a transaction with an extremely low network fee, you can adjust the “Transaction deadline” setting on the Uniswap interface to give your transaction more time before it times out.
You don’t have enough tokens or ETH for the transaction you’re trying to make
A very simple reason why your transaction is failing could be that you don’t have the sufficient funds. When you’re using Uniswap, you’re interacting with a smart contract on the Ethereum blockchain, which requires a fee to be paid with ETH. If you don’t have a sufficient amount of ETH in your wallet to pay this transaction fee, you won’t be able to make a trade through Uniswap.
In some cases, there can be extreme spikes in Ethereum transaction fees due to heightened demand. If the fees for your Uniswap trade seem abnormally high, consider waiting a couple of hours for gas prices to come down to more reasonable levels.
On a related note, you could also be trying to make a swap that you don’t have enough funds for. Check how many tokens you have in your wallet and adjust the swap size accordingly.
Some types of tokens are not supported by Uniswap. For example, any transaction you try to make on Uniswap with a deflationary token will fail.
Other types of Uniswap errors
There are other errors you can encounter while using Uniswap besides the "swap failed" error. If you're trying to swap tokens that have a fee on every transfer or tokens that have a rebasing mechanism, you might get the "UniswapV2: K" error. This error means that you attempted to make a trade which would leave the liquidity pool with fewer reserves than expected by the Uniswap protocol. In such scenarios, the transaction is automatically reverted.
Another example of a less common Uniswap error is the "UniswapV2: TRANSFER_FAILED" error. According to the Uniswap documentation, this error is usually caused by scam tokens which are programmedso that the token can be bought, but not sold.
The bottom line — Slippage is the most common reason for failed Uniswap transactions
If you’re wondering why you’re getting “swap failed” errors on Uniswap, the most likely reason is likely that the trade has higher slippage than what your settings allow for. To remedy this issue, increase the maximum slippage setting, but be careful to not adjust it too high. Another issue could be that you are not paying enough in network fees, which causes the transaction to time out.
Another common error encountered by users on Uniswap and similar decentralized exchanges is the “insufficient liquidity for this trade” error. If you want to learn how to fix it, check out our article explaining why the error happens and what you can do about it.
FAQs
Why does my swap keep failing?
Your swap on Uniswap might be failing for a variety of reasons. Here’s the most common issues and how to fix them:
- Your max slippage settings are too low: Adjust the setting to allow for higher slippage.
- The transaction is timing out: Pay a higher network fee or set a longer transaction deadline in the settings.
- You have insufficient funds: Check if you have enough ETH in your wallet to pay the transaction fee.
Why can’t I buy on Uniswap?
The most common reason why users’ Uniswap transactions fail is slippage. Slippage is the difference between the expected price of a trade and the price at which the trade actually executes. The higher the slippage is, the worse deal you are getting.
Uniswap has a setting that protects users by not performing trades above a certain level of slippage. However, you can adjust the maximum amount of slippage you’re willing to tolerate. By increasing the permitted level of slippage, you’ll likely be able to complete the transaction. Still, you should be careful about increasing the slippage tolerance and you should only do so in small increments.
