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December 5, 2022
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Blockchain: what are unconfirmed transactions?

Transactions that are sent to the blockchain are initially classified as ‘unconfirmed’, however, do you know what this really means?

A blockchain is made up of blocks connected to each other and these blocks contain transactions. To be valid, a transaction must be inserted into a block and at least one other block must be added to the blockchain.

In fact, when a user sends cryptocurrencies to a public address, the transaction is not immediately inserted into the blockchain because it must be validated.

Inside the validation process

Depending on the consensus protocol used by each blockchain, validation involves different procedures. On the Bitcoin blockchain, for example, and all based on Proof-of-Work, miners perform this validation.

Taking the example of Bitcoin, the transaction is initially sent to the call mempool, which is a type of temporary repository of transactions that are waiting to be inserted into a block and then confirmed.

With regard to Bitcoin, the mempool there are always thousands of transactions, reaching even tens of thousands of them waiting for validations, which causes possible congestion.

Miners use this mempool to verify that the transactions are correct, that the digital signature matches the signature of the sender, and to confirm what fees need to be paid to them.

In fact, the fees set by the sender are what determine which transactions miners choose to confirm.

Considering this, a blockchain from the Bitcoin blockchain cannot allocate more than 3,000 transactions. Since the average is one block mined every 10 minutes, it is logical to imagine that the mempool bitcoin is always full and often contains more transactions than there is in a block.

As a result, miners are forced to choose which transactions to include and generally opt for those with the highest rates.

This means that if the fees set by the sender are very low, the transaction not only runs the risk of not being selected for the next block and consequently being confirmed in a few minutes, but also runs the risk of not even being included in the next block.

For that reason, there are thousands upon thousands of unconfirmed transactions, and sometimes they have to wait several days for a miner to agree to validate them.

Choosing intuitive wallets

It is worth remembering that a transaction sent to mempool is not completed and can be canceled or modified. For example, fees can be increased to make it more attractive to miners.

Unfortunately, not all portfolios support such features, especially those managed by third parties.

In reality, the best portfolios are those that give users the fees to specify so that their transactions are included in the next block or at least one of the next 5 or 10 blocks. Thus, they can choose how much to spend on transactions according to their needs.


Therefore, a transaction is not considered valid until it is confirmed because it is included in a block, so unconfirmed transactions are those that are still awaiting validation.

We must remember that the more confirmations it has, the more secure it is. Therefore, it is not recommended to consider a transaction that only has a confirmation as ‘final’.

For more confirmations, simply wait until more blocks are mined after the block in which it is included.

Source: Cryptonomist

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