Fractal Bitcoin Addresses Incomplete Block Filling Due to High-Fee MULTISIG Transactions

On September 27, Fractal Bitcoin addressed user feedback concerning incomplete block filling on their mainnet via a social platform announcement. An immediate investigation revealed that this issue primarily arises due to miners prioritizing high-fee transactions, constrained by two main block size limits: the maximum block size in bytes and the maximum number of SIG operations.

When numerous high-fee MULTISIG transactions occur, the block can hit the SIG limit of 80,000, preventing further transactions from being included. While Segregated Witness (SegWit) transactions typically use 1 SIG, allowing a block to theoretically hold up to 80,000 transactions, this limit is seldom reached in practice. In contrast, MULTISIG transactions consume 84 SIG, reducing the maximum transactions in a block to about 952, leaving block bytes partially unfilled.

Moreover, blocks containing non-MULTISIG low-fee transactions fill the remaining 75% of block space, leading to an approximate 20% increase in total block fees. This scenario is inherent to the BTC mainnet’s existing structure rather than a flaw in the Fractal browser. Fractal Bitcoin assured continuous monitoring and efforts to enhance network connectivity and performance.