Blob expansion goes live as Ethereum targets lower rollup costs
Ethereum increased its per-block “blob” capacity to 21 on January 7, 2026, activating the second Blob Parameter-Only (BPO2) fork on mainnet. The change raises the network’s temporary data space used by rollups and is intended to lower Layer-2 transaction costs by letting L2s batch more data per block.
The adjustment follows December’s first blob parameter fork, which lifted the maximum from 15 after the Fusaka upgrade introduced lightweight, blob-only parameter changes. Today’s step moves the max from 15 to 21 and sets the target near 14 blobs per block, increasing throughput available to rollups without a full client upgrade.
Developers framed the cadence months in advance: core contributors discussed a two-step increase, first to 15 and then to 21, as part of a series of small “BPO” forks designed to scale data availability safely. Community tooling flagged the BPO2 activation shortly after 01:01 UTC on Jan. 7, with trackers reflecting the new target and max settings.
Blobs, introduced with EIP-4844 (proto-danksharding), provide a low-cost, short-lived data channel for rollups. By expanding blob capacity while keeping base-layer execution unchanged, Ethereum can accommodate higher L2 demand without immediately touching gas limits or block times. Research and explainers emphasize that higher blob headroom should ease L2 fees during busy periods by reducing competition for blobspace.
Ahead of Fusaka, contributors signaled this path: “We can go ahead with a Max blob count of 15 for BPO1 and 21 for BPO2… There are a total of 5 BPOs planned for Fusaka,” an ethPandaOps note summarized when the schedule was set in September 2025. Today’s increase aligns with that roadmap.
Background: the Fusaka hard fork (December 2025) established the mechanism for blob-only parameter changes and kicked off the first capacity bump. Coverage and developer briefings outlined BPO2 for early January to complete the initial scaling tranche, with further blob tuning possible in 2026 if demand warrants.
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