Hi Andrew,

> Restricting it to OP_RETURN would have zero effect on people trying to use scriptpubkeys for data storage.

1. The data shows that nobody is using scriptPubKeys for more than 520 bytes. In fact, people have found new ways to encode data in transactions. Example: [Merkle path][0] in taproot control block

2. If this applies to all scriptPubKeys, it could negatively affect the [UTXO set][1] size because multiple outputs is an alternative if someone really wants to use scriptPubKey for data.

[0]: https://mempool.space/tx/c5714af322cd2ba94adf3d74325eb17f03d029ad2bf47dc54c3d929833c02628
[1]: https://mainnet.observer/charts/utxoset-size/

/dev/fd0
floppy disk guy

On Fri, Oct 3, 2025 at 7:29 PM Andrew Poelstra <apoelstra@wpsoftware.net> wrote:

On Thu, Oct 02, 2025 at 06:21:18PM -0700, /dev /fd0 wrote:
>
> We can't predict future usage,

Aside from proof-of-publication (i.e. data storage directly in the UTXO
set) there is no usage of script which can't be equally (or better)
accomplished by using a Segwit v0 or Taproot script.

> so it would be great if this was restricted
> to OP_RETURN. While there is no real use for a scriptPubKey larger than 520
> bytes as shown in the data you shared, it is possible that users may create
> more OP_RETURN outputs after this change. It does not affect the UTXO set
> but will cost more and economically discourage the use of multiple
> OP_RETURN outputs.
>

Restricting it to OP_RETURN would have zero effect on people trying to
use scriptpubkeys for data storage. They would switch to any of the 65
or so other OP_RETURN equivalents, and failing that, switch to
OP_RESERVED, then to OP_FALSE, then to `0 1 EQVERIFY`, and so on. A
restriction that applies specifically to OP_RETURN outputs is no
restriction at all.

--
Andrew Poelstra
Director, Blockstream Research
Email: apoelstra at wpsoftware.net
Web: https://www.wpsoftware.net/andrew

The sun is always shining in space
-Justin Lewis-Webster