QR encoded transactions that embed a payload and post it onchain?

[MadCake]

I have been banging my head for a couple of days here.

I want to be able to generate a QR code that is recognised widely by bitcoin wallets, representing a transfer with an embedded onchain message.

At the moment I am using OP_RETURN for this. My code looks good but I am hitting a wall, because no QR code I generate is recognized by wallets like Blockstream Green. I have tried using BIP21 with a message field but if I understood correctly, that does not post the data onchain, and it is a hard requirement that the data is posted onchain - this worked with Green, but I have not tried with others.

Then I have been trying PSBT, but apparently I need the user to provide me with their sender address prior to this to build in this format, which is also a no-go, introduces too much friction in the UI.

What other options do I have? I need something that is widely adopted by wallets in the ecosystem.

[ABCbits]

What other options do I have? I need something that is widely adopted by wallets in the ecosystem.

Probably none, partly because many wallet don't have feature to create OP_RETURN output.

But FWIW, BIP 321 is probably closest thing you're looking for. It has message key[1], but it's very likely it refer to message shown on user device. So what you could use is otherparam, that could be used for your purpose and suggest other wallet to support your key/otherparam.

[1] https://github.com/bitcoin/bips/blob/master/bip-0321.mediawiki#query-keys
[2] https://github.com/bitcoin/bips/blob/master/bip-0321.mediawiki#abnf-grammar