How Do SegWit and Other Scaling Solutions Aim to Reduce Transaction Fees?

Segregated Witness (SegWit) and other scaling solutions aim to reduce transaction fees by increasing the effective capacity of each block. SegWit does this by moving signature data (the largest part of a transaction) out of the main block and into a separate structure.

This frees up block space, allowing more transactions to fit into a single block. By increasing the supply of block space, the competition for that space decreases, thus lowering the transaction fees.