A real soft fork changing Bitcoin's consensus rules as you read this. The perfect illustration of how consensus and relay interact in practice.
BIP110 is a temporary soft fork that reduces the OP_RETURN data limit.
OP_RETURN is a Bitcoin Script opcode that allows a small amount of data to be embedded in a transaction. Since its introduction in 2014 (OP_RETURN limit of 80 bytes), it's been used for everything from colored coins to timestamps to token protocols.
Over time, the data embedded in Bitcoin transactions has grown. With the rise of inscriptions (via Ordinals), some blocks now contain significant amounts of arbitrary data — pushing the network toward being a data storage layer rather than a monetary network.
The change: BIP110 reduces the maximum OP_RETURN data size from 80 bytes to 1 byte (effectively empty) for a temporary period of ~1 year. After that, the limit reverts back to 80 bytes.
"BIP110 doesn't remove the ability to put data in Bitcoin transactions. It temporarily tightens the limit to discourage the data storage use case while the community debates a permanent solution."
BIP110 changes a consensus rule. Specifically, it modifies the script verification rules:
80 bytes of OP_RETURN data per output.1 byte of OP_RETURN data — effectively disabling OP_RETURN for data storage.55% of blocks in a 2,016-block retarget period.Because it's a soft fork, old nodes that haven't upgraded will still accept BIP110 blocks. The rule is tighter, so old nodes see the new blocks as valid (they don't check the OP_RETURN limit as strictly, so they pass the less restrictive check).
BIP110 proves that consensus rules CAN change — but only through a deliberate, transparent, multi-month process. Version bit signaling lets the network see miner support in real time. Nodes choose to upgrade. There's no "emergency decree" — just voluntary adoption by node operators and miners.
Here's where the Two Rulebooks framework shines. BIP110 changes a consensus rule, but your relay policies still apply independently:
| Situation | Consensus Says | Relay Says (Your Choice) |
|---|---|---|
| An inscription transaction arrives | Valid, if OP_RETURN ≤ 80 bytes | You choose: relay it, skip it, or log it |
| After BIP110 activates | Valid, if OP_RETURN ≤ 1 byte | Your relay policy unchanged — it just sees fewer large-data transactions to handle |
| After BIP110 activates: an unupgraded old client sends 80 bytes of OP_RETURN (valid under old rules) | REJECTED — violates new ≤1 byte limit | N/A — rejected at consensus layer before relay is checked |
The important point: once the consensus rule changes, your relay policy doesn't need to adapt. The tighter rule at the consensus layer means fewer data-heavy transactions exist to be relayed. Your relay settings continue to do what they always did — only now they handle less data traffic.
A node operator who disagrees with BIP110 can choose to run pre-BIP110 software. Their node will still work (since BIP110 is a soft fork), but they'll be on a chain that enforces the old rules. This is the ultimate protection: your node, your consensus choice.
BIP110 is happening right now. You can watch the countdown tick down on the BIP110 page. Here's what it demonstrates about Bitcoin's rule architecture:
1. Consensus changes are transparent. Every step — proposal, signaling, activation — happens in public. Version bits let anyone check miner support block by block.
2. Soft forks protect the network. Old nodes don't break. They just see fewer things. The network upgrades organically, not by fiat.
3. Relay policies remain sovereign. Your node's fee filters, mempool limits, and peer preferences are untouched by BIP110. The consensus layer tightened, but your local settings are still yours.
4. Temporary rules test permanence. BIP110 is designed to auto-revert after ~3 months. This is unprecedented — a temporary soft fork. It shows that Bitcoin can experiment with rule changes without committing to them forever.
"The Nixon Shock changed the rules permanently and without warning. BIP110 changes a rule temporarily and after months of public debate. These are not the same kind of system."
| Dimension | Nixon Shock (1971) | BIP110 (2026) |
|---|---|---|
| Notice | 0 days — announced on TV | Months of public BIP discussion, signaling |
| Decision maker | One president | ~Thousands of node operators + miners |
| Scope | Changed the world's monetary system | Changed one opcode limit temporarily |
| Permanence | Permanent (still in effect today) | Temporary (~3 months, auto-reverts) |
| Dissent option | None — the law applied to everyone | Run pre-BIP110 software on your chain |
| Verification | Trust the government | Verify with your own node |
The contrast is the entire point of Bitcoin. The Nixon Shock was possible because the rules were policies, not laws. BIP110 is possible because the rules are laws — and changing them requires broad, transparent, voluntary consensus.