The transaction can be of two types
- Transactions that are used for just transferring funds from one EOA to another.
- Transactions that carry a payload of data along with an amount of ether.
The most usual case when the first case fails is when the transaction goes out of gas. i.e., When the gas limit set is lower than the network fee at that point in time.
For transactions that carry data with it, There are a couple of ways it could fail.
If the transaction invokes a method in the smart contract and an error occurs in one of the lines or if a requirement throws or assertion fails, The transaction fails.
A transaction that deploys a contract could fail if there are any errors that come up while executing the lines in the constructor.
A transaction which transfers ether from a contract to another EOA could fail if the contract doesn't have enough ether to transfer or if the gas supplied to execute the method which contains the transfer is insufficient.
If the transaction from one EOA to another fails, then that is pretty straightforward that its gas. In case the failed transaction involves a smart contract, then we need to debug the contract.