What Is BIP-110? The Reduced Data Temporary Soft Fork Explained

But with less than 1% of mining hashrate signaling support as of late June 2026, a UASF (User-Activated Soft Fork) mechanism threatens to trigger a chain split by September 2026 . Here's everything you need to know about BIP-110, its goals, activation mechanism, opposition, and what happens next.

What BIP-110 Actually Proposes

The stated purpose of BIP-110 is to "temporarily limit the size of data fields at the consensus level, in order to correct distorted incentives caused by standardizing support for arbitrary data, and to refocus priorities on improving Bitcoin as money" . Concretely, it would impose seven consensus-level restrictions:

• New transaction outputs limited to 34 bytes (except OP_RETURN)
• OP_RETURN outputs capped at 83 bytes, restoring the historical limit
• Data pushes within scripts capped at 256 bytes
• Spending from undefined Taproot witness versions blocked
• Witness elements capped at 256 bytes
• Additional restrictions on large non-monetary data patterns

Inputs spending UTXOs created before activation are permanently exempt, so pre-existing funds remain spendable .

Two Paths to Activation

BIP-110 includes two separate activation mechanisms :

• Path 1 — Miner-activated soft fork (MASF): Miners signal support using bit 4 in their block headers. If 55% of blocks signal within a single difficulty retarget period (~2 weeks, or 2,016 blocks), BIP-110 locks in and activates one retarget period later. This would be the smooth, voluntary route.
• Path 2 — User-activated soft fork (UASF): If the 55% threshold is not met, nodes running BIP-110-compatible software (primarily Bitcoin Knots forks) enter a mandatory signaling phase starting at block 961,632 (projected early August 2026) and running through block 963,647. During this window, those nodes reject non-signaling blocks as invalid. Unconditional activation then triggers for all BIP-110 nodes at block 965,664 (~September 2026) .

Miner Support: Below 1% of Hashrate

As of late June 2026, BIP-110 miner support remained negligible :

• ~0.31% of total hashrate (~5 EH/s out of approximately 940 EH/s total), according to Bitget .
• News.Bitcoin.com corroborated the same figure of roughly 5 EH/s signaling (less than 1% of the network) .
• The handful of signaling blocks came from small mining groups: BIP110, Roughnecks110, and 234 Alberta .
• No major pool (Foundry, Antpool, F2Pool, Binance Pool, ViaBTC) has signaled support .

The 55% early lock-in threshold appears extremely unlikely to be reached voluntarily before the August UASF window .

Who Opposes BIP-110 — and Why

BIP-110 has drawn opposition from some of the most prominent figures in Bitcoin:

• Adam Back (CEO, Blockstream; cited in the Bitcoin whitepaper) called it "a literal downgrade" and a "regression" — arguing it breaks Bitcoin's neutrality, invites censorship risks, and that the cure is worse than the disease . He also warned it could undermine Bitcoin's immutability .
• Jameson Lopp (CTO, Casa) labeled the proposal "reckless and doomed" and warned it could trigger a persistent chain split, citing the Bitcoin Cash and Bitcoin SV splits as cautionary examples .
• Wang Chun (co-founder, F2Pool) called BIP-110 "a bunch of nonsense" .
• Michael Saylor (co-founder, MicroStrategy) called BIP-110 "Bitcoin's biggest self-inflicted risk" and warned it threatens the network's stability and narrative .

The core opposition argument is that restricting data at the consensus level amounts to protocol-level censorship, breaks Bitcoin's principle of permissionless transactions, and risks a catastrophic chain split if BIP-110 nodes and non-BIP-110 nodes disagree on which chain is valid .

What Happens if the 55% Threshold Is Not Reached

If voluntary lock-in does not occur :

• The UASF mechanism triggers at block 965,664 (~September 2026), at which point BIP-110 nodes and non-BIP-110 nodes split into two separate chains.
• All major mining pools are expected to stay on the non-BIP-110 (Bitcoin Core) chain, which retains ~99%+ of hashrate. The BIP-110 chain would be an extremely low-hashrate minority fork — effectively an altcoin spun off from Bitcoin .
• BIP-110 supporters acknowledge this dynamic: one supporter noted, "Core chain keeps all hashpower. BIP110 fork stalls unless miners move" — and consider it a legitimate UASF expression of node preferences .
• Risk of replay attacks, exchange confusion, and ecosystem disruption during the split period is acknowledged by both sides .

The Other August 2026 Fork: eCash

Separate from BIP-110, veteran Bitcoin developer Paul Sztorc (founder of LayerTwo Labs) announced a hard fork called eCash, scheduled for block height 964,000 in August 2026 .

Key differences from BIP-110:

• It is a hard fork, not a soft fork.
• Every BTC holder at the time of the fork receives eCash on a 1:1 basis .
• The fork activates BIP-300/BIP-301 ("Drivechains"), a sidechain scaling solution Sztorc has championed for nearly a decade .
• The most controversial element: Sztorc proposed reassigning fewer than half of Satoshi Nakamoto's ~1.1 million BTC on the eCash chain to early investors — a move no previous Bitcoin fork has attempted .

Note on naming: There is already a pre-existing token called eCash (ticker: XEC) from a 2021 Bitcoin Cash fork, creating potential ticker confusion .