What happens to a Bitcoin transaction before it gets its first confirmation?
Correct answer
Answer A: It is sent to the network, checked by nodes and can then be included in a block.
Quick explanation
First, the transaction spreads through the network. Once a miner includes it in a valid block, it receives its first confirmation.
Detailed explanation
A Bitcoin payment usually starts in the wallet. It selects suitable UTXOs as inputs and sets the recipient output, any change output and a fee. It then creates the required signatures. Only now is the transaction fully authorized.
The wallet or a connected node broadcasts the transaction to peers. Each receiving node checks format, signatures, available inputs and conflicts, among other things. If accepted under its consensus rules and policies, the transaction may enter its local mempool and be relayed onward.
Miners or mining pools select transactions from their local view for a candidate block. If they find valid proof of work, they broadcast the block. Full nodes then check not only the proof of work but also the block structure and every included transaction. Only a valid block is appended to the local best chain. The payment thereby receives its first confirmation. Further blocks built on it increase the confirmation count.
Not every validly created transaction is confirmed immediately. Fee conditions, relay, local policy and competing transactions can affect the process.
Example or everyday application
A wallet creates a low-fee payment in the morning. Nodes accept it into their mempools, but only a later miner includes it in a block. From that point, the wallet shows one confirmation.
Common misconception
Many beginners combine wallet signing, node verification and miner inclusion into one step. Signing, checking and inclusion in a block are separate steps in a time sequence.
Sources used
Bitcoin Developer Guide – Transactions
This source is mainly intended for developers. The relevant information may therefore be harder to find.
Check original sourceBitcoin Developer Guide - Block Chain
This source is mainly intended for developers. The relevant information may therefore be harder to find.
Check original source