How Does Block Size Limit Affect the Confirmation Chances of a Zero-Fee Transaction?

The block size limit significantly reduces the confirmation chances of a zero-fee transaction by creating scarcity for block space. Because the space within a block is finite, miners must choose the most profitable transactions to include.

A zero-fee transaction provides no profit, so it is the first to be excluded when the block is full of fee-paying transactions. In a high-demand network, the limit ensures that only transactions paying a competitive fee rate are confirmed, pushing zero-fee transactions out of the mempool and confirmation queue.