According to BitMEX Research, OP_Return2 is a proposed Bitcoin (BTC) transaction output that commits a hash to up to 8MB of arbitrary data while nodes are not required to have that data to validate blocks, so miners and full nodes do not need to validate, relay, or store the extra data (source: BitMEX Research on X, Oct 9, 2025). OP_Return2 would be implemented via a softfork that changes the block weight formula to 8 times base data plus 2 times witness data plus claimed OP_Return2 data store being less than 8 million units (source: BitMEX Research on X, Oct 9, 2025). Special full data archive nodes could optionally relay and store the extra arbitrary data if available, while consensus rules would only require specifying the amount of extra data, and a fee to miners would be paid based on the specified data amount (source: BitMEX Research on X, Oct 9, 2025). Potential disadvantages highlighted include unclear willingness to pay for extra data when miners and nodes are not storing it, limited added value compared with OpenTimestamps with higher per-byte cost, and questions over whether a softfork is necessary given existing hash-in-chain plus external storage approaches (source: BitMEX Research on X, Oct 9, 2025). BitMEX Research also cautions that extra spam data could outbid legitimate payment transactions due to a steeper fee discount per byte, with an 8MB per-block size limit enabling 8MB of spam images to compete at the same cost as a 4MB Taproot witness inscription (source: BitMEX Research on X, Oct 9, 2025).