How to avoid "This gas fee has been suggested by" message in MetaMask using web3js

Question

I'm currently in the process of upgrading an Ethereum dApp (using React JS) to conform to the new EIP-1559 standard (A.K.A. the London hard fork). The app uses web3.js (v1.5.2) to initiate transactions which take on a form something like

const contract = new web3.eth.Contract(
  contractABI,
  CONTRACT_ADDRESS,
);

await contract.methods
  .deposit(recepient, amount)
  .send({ from: account, value })

We encourage users to interface with our app using MetaMask.

Despite the fact that I neither specify a gasPrice, gasLimit, nor the equivalent maxPriorityFeePerGas or maxFeePerGas specified by EIP-1559 when a transaction is sent, MetaMask still warns (on my local test environment) "localhost suggested gas fee" with "Unknown processing time" and a potentially huge fee.

On clicking "Edit" another warning message appears, to make matters worse, the values I (or I guess web3) supposedly "suggested" are not reasonable according to MetaMask's estimate.

Is there any way using web3 interfacing with MetaMask to accept MetaMask's suggested values, removing these MetaMask warnings and insuring that the fees are calculated correctly? I notice looking at https://app.uniswap.org/ that although MetaMask still shows the first "app.unswap.org suggested gas fee" warning, the txn time is correctly calculated and clicking on "Edit" does not present any further warnings. Is Uniswap's more reasonable interaction with MetaMask replicable using web3.js?

score 19 · Accepted Answer · edited Mar 28 '22 at 03:25

19

OK, so I've figured this one out.

If maxPriorityFeePerGas and maxFeePerGas are not defined for a particular transaction, web3 will generate its own values. Disappointingly, the generated values are pretty poor and will trigger warnings in MetaMask. The solution (at the point of writing completely undocumented) is to set maxPriorityFeePerGas and maxFeePerGas to null instead of undefined. This will signal to web3 that you don't want it to pass the provider these values.

So the code should look something like:

const contract = new web3.eth.Contract(
  contractABI,
  CONTRACT_ADDRESS,
);

await contract.methods
  .deposit(recepient, amount)
  .send({ 
    from: account, 
    value, 
    maxPriorityFeePerGas: null,
    maxFeePerGas: null, 
  });

Also, ensure that you're using the latest version of web3, since EIP-1559 support was only added in v1.5.

edited Mar 28 '22 at 03:25

Pang

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answered Aug 26 '21 at 09:45

Joel Collins

429
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10

I can confirm that adding these fields solves 'Unknown processing time' warning message – mhrsalehi Nov 25 '21 at 10:06
Adding the two fields set to 'null' does get rid of the 'This gas fee has been suggested by' message, however the gas fees in MetaMask are still upwards of $10,000. For a similar transaction in Uniswap they are about $72 at the moment. What could be causing this ridiculously high estimate? I'm not specifying any gas fees in my code. – jspru Nov 26 '21 at 13:20
Update - the following settings made things a little more reasonable for me: resp = await faucetContract.methods.withdraw().send({ from: accounts[0], gas: 300000, gasPrice: null, }) – jspru Nov 26 '21 at 13:48
I think it's not documented because it's likely a bug in web3.eth.Contract. – Dave Sumter Apr 17 '22 at 09:29
1

Very useful! Can confirm this trick still works in Apr 2023 – Paintoshi Apr 13 '23 at 08:27
Doing this is perfect if you want to use the "Market" gas price in MetaMask without pre-calculating the gas fees yourself. – Alexandre Desroches Apr 25 '23 at 01:50

How to avoid "This gas fee has been suggested by" message in MetaMask using web3js

1 Answers1