A token fee is the amount that a token charges when you buy, sell, or transfer it.
Tokens that charge fees are also known as fee on transfer tokens. These fees are set and collected by the token issuer. Uniswap Labs does not receive any share of these fees.
If the token you are swapping has a buy or sell fee higher than 0.00%, then the token charges a fee when bought, sold, or transferred. You may see a token warning when interacting with the token on the Uniswap interface.
Tokens that charge a fee do not allow any swaps to occur unless the buy and/or sell fee is paid.