Are you saying that zero amount UTXOs are retained in the UTXO set?

Mostly right, but…

> Any non-zero unspent transaction output that is not provably unspendable.

…UTXOs are allowed to have an amount of 0 per consensus rules, the dust limit is also just a mempool policy.

Murch

Any non-zero unspent transaction output that is not provably unspendable.

 is provably unspendable, so it can be pruned.

But an output with a fake public key or fake script hash (such as produced by STAMPS) is unspendable, but that's not always obvious. Thus these outputs must be retained in the UTXO set. These are the most harmful ones.

bitcoin

Quick questions about OP_RETURN? Quick answers here.

tidwell

> What makes a UTXO unprunable?

Any non-zero unspent transaction output that is not provably unspendable.

An output script starting with `OP_RETURN` is provably unspendable, so it can be pruned.

But an output with a fake public key or fake script hash (such as produced by STAMPS) is unspendable, but that's not always obvious. Thus these outputs must be retained in the UTXO set. These are the most harmful ones.