Tutorials:Swap tokens for Pol Using Uniswap

Swap Tokens for POL in Uniswap

Let's swap 105 Winter tokens for POL using Uniswap, and compare it to the same transaction using Metamask. You will notice that Metamask is a bit more expensive. They claim that your transactions are safer using their own tools that can minimize price slippage.

Including the price slippage caused by trading bots that try to exploit the decentralized market making formula. We will talk more about these "front running bots" in the next quest.

• Go to Uniswap

Transaction in Metamask

Let's get the Metamask quote for this transaction:

Notice:

• The quote: 1 Winter = 0.0080 POL includes a 0.875% Metamask Fee.
• Metamask will enable Winter for Swapping.

Transaction in Uniswap

With Metamask connected to the Polygon network, visit Uniswap and click on connect wallet:

After confirming the connection, click on select token (see the orange arrow)

In Metamask, let's copy the Winter contract address:

And paste it in the search tokens field:

Warning:

Anybody can create a smart contract or token and call it Winter or Bitcoin, there are no authorities regulating the Open Source programming. Therefore it is very important that you know exactly the contract address of the assets.

Here we can confirm that this is the right contract because the Uniswap window shows the correct Winter amount we are swapping.

And select POL for the destination, and get Uniswap quote:

Notice we get a slightly better price, not very important in these small transactions.

Now we will confirm and swap. This will be done in 3 steps:

1. Approve in Wallet (Metamask did this step more automatically)
2. Sign Transaction
3. Confirm the Swap

You only have to authorize Uniswap to use Winter tokens once. 

Now give permissions to withdraw the tokens:

At this point we have authorized Uniswap to spend AND withdraw the tokens, now finally you can do the swap:

By then prices may have changed, even significantly, so this is the final confirmation to go on with the transaction:

Let's review the transaction in the Activity tab:

Click on the transaction and select: View on Block Explorer.

Conclusion

We obtained a slightly better price in Uniswap, and it cost less gas as well. This is not very important for such small transactions, sometimes, specially if you are swapping POL for tokens (buying tokens), the price slippage may be a problem and paying a little more in Metamask may be justified.

Always pay attention to the last "confirmation" message from Metamask, prices may have varied significantly since you receive the quote and execute the transaction. This "price slippage" can be exploited by people and trading bots as we will see in the next quest.

Task:

Using the transaction hash:

0xa991445bf93b48ff09c8c154e8d386b4513f3925ecc526f551fdd53a0c8ed7da

Go to PolygonScan and find the contract address of Uniswap Universal Router (V1 2 V2 Support).