Why Is My 2nd ETH Transaction Dropped

When you trigger the 1st outgoing ETH transaction, it will be sent to the mempool waiting to be processed by the miners. The pending time will depend on the amount of the transaction fee and the traffic of the chain. If you trigger another outgoing ETH transaction (2nd transaction) during this pending period, it will be automatically dropped as for Ethereum, you cannot have a transaction with a nonce of 1 mined before one with a nonce of 0.

What is a nonce?

In Ethereum, every transaction has a nonce. The nonce is the number of transactions sent from a given address, and it can only be used once. In cryptography, a nonce is a one-time code selected in a random or pseudo-random manner that is used to securely transmit the main password, preventing replay attacks.

Each time you send a transaction, the nonce value increases by 1. There are rules about what transactions are considered valid transactions, and the nonce is used to enforce some of these rules. Specifically:

  • You cannot have a transaction with a nonce of 1 mined before one with a nonce of 0. 
  • You cannot have a transaction with a nonce of 2 mined if you have not already sent transactions with a nonce of 1 and 0.

Please refer to the following diagram for more details: