One way to deal with the BIP34 does not imply BIP30 issue, aka the Block 1,983,702 Problem, is a soft-fork that makes the SegWit commitment mandatory. [0]

There are no OP_RETURN outputs in any of the coinbase transactions before BIP34 activated (unless my script is wrong [1]), let alone OP_RETURN outputs starting with the SegWit magic bytes 0x6a24aa21a9ed.

Nowadays OP_RETURN outputs in the coinbase transaction are very common, used not just for the SegWit commitment, but also by sidechain(ish) protocols.

When was the first instance of this?

[0] https://twitter.com/kcalvinalvinn/status/1733008287887659266

[1] https://gist.github.com/Sjors/018f764b28efdf29fda60e47f19615a5


1 Answer 1


The first coinbase transaction that has an OP_RETURN output is in block 246816. The transaction has 288 outputs in total, and the OP_RETURN is the last one.

  • Thanks! How did you find it? Commented Dec 20, 2023 at 11:38
  • 3
    I wrote a script that goes through every block in order until it finds one whose coinbase transaction has an output whose output script starts with the byte 6a. Commented Dec 20, 2023 at 12:35
  • BIP30 kicked in on 2012-03-15, BIP34 at 227,835 on 2023-03-24. Block 246,816 was mined four months later on ‎2013-07-16. Commented Apr 5 at 17:18

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