-
@ Itamar Peretz
2025-05-23 19:30:06
Evidence of real-world abuse Bitcoin Core’s 0.9 release notes—quoted in the OP_RETURN controversy gist https://gist.github.com/andy108369/dadc7d1f93edca5a775f29ca1bf12065 —state that OP_RETURN and its size cap were added “to avoid data-storage schemes … storing arbitrary data … as forever-unspendable TX outputs, bloating Bitcoin’s UTXO database.” That is Core itself confirming that users were already broadcasting cheap, never-spendable outputs to impose long-term costs. You can read more here as well:
https://research.mempool.space/utxo-set-report/
https://blossom.primal.net/7f8421fe763b68e8c6a007f40f8f905beaebf73f9cc64e219b622de46c7bc246.png
Why the 80-byte cap still matters even though OP_RETURN is prunable . OP_RETURN fixed where the data lives (no UTXO pollution), but the cap limits how much can be shoved into each transaction when fees are low. Without it, a quiet mempool allows anyone to pad blocks with hundreds of kilobytes of inert data for a small fee; every future node must then download, hash, and store those bytes forever. The cap is a light “speed bump” that raises the minimum fee per byte of non-monetary payload until the broader fee market (full blocks) takes over, discouraging bulk dumps while leaving ordinary 20–80 byte commitments untouched.
Provably unspendable vs “looks spendable” True OP_FALSE OP_RETURN outputs never hit the UTXO; the historical bloat came from payloads hidden in outputs that looked spendable. If the cap disappears, data senders can again choose between unlimited OP_RETURNs (if nodes relax their policy) or reverting to fake-pubkey tricks (if nodes refuse to do so). Either path reopens the very pressure that Core 0.9 tried to defuse.
On your Pi’s disk I/O , Modern bitcoind keeps hot UTXO slices in cache, so today’s writes are small. The worry is cumulative: each cheap data dump becomes a permanent addition that the next wave of low-cost nodes must sync and store, gradually raising the hardware floor, even for people who never interact with OP_RETURN.
Bottom line: the fee market prices block space once blocks are full; the 80-byte cap stops low-fee hours from turning every block into a bargain-rate data dump and quietly lifting the entry cost for future node operators.