For the first time since the blocksize wars of 2017, Bitcoin is heading into a genuinely contested change to its consensus rules — on a clock. BIP-110 is a proposal to temporarily tighten what counts as a valid Bitcoin block, aimed at squeezing out the non-financial "spam" data that has filled the chain since the inscriptions era. Its activation window closes around September 1, 2026, whether miners embrace it or not. Michael Saylor calls it "a bad idea." Its supporters call it a rescue of Bitcoin's monetary purpose. This guide explains what the proposal actually does, how activation works, what the fight is about, and — most practically — what any of it means for your coins.

What BIP-110 actually proposes

BIP-110 is a temporary soft fork: a one-year tightening of Bitcoin's consensus rules that would add seven new restrictions on transactions in newly mined blocks — chiefly caps on the size of data-carrying fields and rejection of certain script patterns used to embed arbitrary data on-chain, per the proposal's own site, bip110.org, and Simple Mining's technical summary. The rules are explicitly sunset-limited: they expire 52,416 blocks after activation — roughly one year — unless the network chooses to renew them.

The word soft matters. A soft fork narrows the rules rather than widening them: every block valid under BIP-110 is also valid under today's rules, so nodes that never upgrade still follow the new chain. What changes is the reverse direction — some transactions that are valid today, including fee-paying ones, would be rejected under the new limits. That asymmetry is precisely what the fight is about.

Why now: the spam wars, briefly

BIP-110 did not appear from nowhere. Since the inscriptions boom began in 2023, Bitcoin's blockchain has carried an ever-growing volume of non-financial data — images, tokens and arbitrary payloads embedded in transaction fields that were designed for other purposes. To supporters of filtering, the results are concrete: a bloated UTXO set that every full node must store forever, higher costs for running the network's most decentralization-critical infrastructure, and fee spikes that price out the monetary transactions Bitcoin exists to serve. The dispute simmered for years at the relay policy level — rules about which transactions nodes forward, which individual operators can set freely. What makes 2026 different is the escalation to the consensus level: rules about which blocks are valid at all. Relay policy is an opinion; consensus is law. That escalation, more than any specific data cap, is what turned a technical disagreement into Bitcoin's biggest governance fight in nearly a decade.

How activation works: 55% signaling or a flag day

BIP-110 departs from recent precedent in two ways. First, its miner-signaling threshold is 55% — far below the 90–95% used for recent upgrades like Taproot. Second, it carries a mandatory flag day: if signaling never reaches the threshold, the rules activate anyway for enforcing nodes, with activation projected for block 965,664, near September 1, 2026, per Bitcoin Poland's governance analysis. In other words, the proposal's designers deliberately removed miners' ability to veto by inaction.

Where does support actually stand? As of mid-July, effectively nowhere among miners: CoinDesk reported miner signaling at zero as the deadline neared, though signaling blocks have since begun appearing, per CoinTrust. The decisive variable is not miners, though — it is how many economic nodes (exchanges, custodians, payment processors, individual node operators) choose to run enforcing software by the flag day.

A 90-second primer: how Bitcoin changes its rules

For newer readers, some context on why this process looks so strange. Bitcoin has no board, no foundation with authority, and no on-chain voting. A Bitcoin Improvement Proposal is just a public document; it becomes reality only when the people running the network's software choose to enforce it. Historically that coordination has been deliberately conservative: SegWit activated in 2017 only after a bruising standoff in which economic nodes threatened to enforce it themselves (the "user-activated soft fork"), and Taproot activated smoothly in 2021 with a 90% miner-signaling threshold precisely to guarantee overwhelming consensus before any rule changed. Against that history, BIP-110's 55% threshold plus a mandatory flag day is a radical compression of the safety margin — its designers argue miners should not hold a veto over users; its critics reply that the margin exists to prevent exactly the contested-activation scenario described below. Both can be true, which is why this is a governance story as much as a technical one.

The case for BIP-110 — and the case against

Supporters argue Bitcoin's purpose is sound, permissionless money, and that years of inscriptions, tokens and arbitrary data have crowded block space, bloated the UTXO set, raised node costs and diverted the chain from that purpose. A one-year, self-expiring filter, in their view, is a proportionate and reversible defense — closer to a relay policy with teeth than a permanent constitutional change.

Opponents — led loudly by Michael Saylor, whose company holds more than 843,000 BTC, and joined by Blockstream's Adam Back, per CoinDesk — argue that the cure is worse than the disease: using consensus rules to invalidate transactions someone dislikes sets a censorship precedent, and fee markets already price spam appropriately. Saylor's formulation:

He followed with a 110-point thread — one point per BIP number — framing the dispute as a test of Bitcoin's neutrality rather than a technical question about data limits:

The alignment of Saylor and Back — corporate treasury's biggest whale and one of Bitcoin's most respected cypherpunk engineers — against a proposal with meaningful grassroots node-runner support is exactly what makes BIP-110 hard to handicap:

The scenarios: what can actually happen by September

Scenario 1 — quiet failure. Economic adoption of enforcing software stays marginal, the flag day passes with only a small minority enforcing, and the new rules exist only on paper for a fringe of nodes. Most likely if exchanges and custodians sit it out. Market impact: negligible.

Scenario 2 — clean activation. Signaling crosses 55% or a supermajority of economic nodes enforces by the flag day; miners follow the fees; blocks obey the new limits for a year. Because it is a soft fork, non-upgraded users notice nothing. Market impact: modest — a governance event absorbed the way Taproot was.

Scenario 3 — the ugly middle. A significant minority — but only a minority — of hashrate and economic nodes enforce. If an enforcing miner rejects a block containing now-invalid transactions while non-enforcing miners build on it, a temporary chain split is possible, with the usual attendant risks: exchanges pausing deposits, wildly divergent fee estimates, and re-org anxiety. This is the scenario that would move price, and it is why the proposal's critics consider a 55% threshold reckless. As TFTC's coverage notes, the lock-in window is where the real fight now is.

What holders should actually do (in most cases: nothing)

Start with the reassuring part: BIP-110 does not touch existing coins. The proposed limits apply to new transactions in new blocks. Nothing in your wallet becomes invalid, no balance changes, and ordinary payments — simple sends between addresses — are unaffected by every one of the seven limits. If you hold BTC through an ETF, your issuer's custodian handles protocol events entirely; as we explained in our ETF custody guide, you own a claim on custodied coins, not protocol exposure.

For self-custody users, the checklist is short. If you run your own node, decide deliberately which software you run through August — that choice, multiplied across thousands of operators, is the vote. If you don't run a node, no action is required, though September's flag-day week is a sensible time to avoid time-critical large transactions in case Scenario 3 produces temporary fee chaos. If you use hardware wallets and multisig, nothing about key management changes — see our self-custody playbook for the fundamentals.

The timeline to watch

  • Now → late August: miner signaling percentage (currently minimal but rising) and, more importantly, announcements from major exchanges, custodians and mining pools about which software they will run.
  • August 2026: the mandatory flag-day arming window arrives; enforcing-node counts become the key public metric.
  • ~Block 965,664, near September 1, 2026: projected activation. Watch for any orphaned blocks in the first days — the tell for Scenario 3.
  • ~52,416 blocks later (late 2027): the rules sunset automatically unless renewed — meaning even full activation is, by design, a one-year experiment.

FAQ: BIP-110

Is BIP-110 a hard fork? No. It is a soft fork — a narrowing of the rules. Old nodes continue to follow the chain without upgrading. The chain-split risk exists only in the contested-minority scenario, and would likely be temporary.

Will my existing bitcoin be affected? No. The limits apply only to new transactions. Balances, existing UTXOs and ordinary payments are untouched.

When would it activate? Via 55% miner signaling, or via mandatory flag day regardless — projected around block 965,664, near September 1, 2026. The rules expire about one year after activation.

Who supports and opposes it? Support comes largely from node operators and developers focused on Bitcoin's monetary use. Opposition is led by Michael Saylor and Adam Back, who argue consensus-level filtering sets a censorship precedent and that fee markets should handle spam.

Should I sell before September? That is a personal decision this guide cannot make. Historically, contested-but-contained governance events have produced volatility windows rather than lasting damage; the 2017 fork year is the extreme precedent. Understand the scenarios, and see the disclaimer below.

Investment disclaimer: This article is for informational and educational purposes only and does not constitute financial, investment, legal or tax advice. Cryptocurrency markets are highly volatile and you can lose some or all of your capital. Always do your own research and consult a licensed financial advisor before making investment decisions.