Ethereum's second BPO hard fork raises blob limit to 21

Ethereum’s second Blob Parameter-Only (BPO) hard fork raised the blob limit from 15 to 21, taking effect on Wednesday at 1:01:11 UTC.

The upgrade increases data throughput by allowing more transactions to be batched via rollups and also raised the blob target from 10 to 14, which is widely seen as the more important metric to watch because consistently approaching the 21-blob limit could overload node bandwidth and storage.

One blob unit fits 128 kilobytes of data, meaning Ethereum can now store up to 2,688 KB in a single block. Blobs boost transaction throughput on layer 2s and help stabilize gas fees on the mainnet as the network becomes less congested; YCharts data shows fees have been far more stable since the first BPO hard fork on Dec. 9, 2025.

Participants at the Ethereum All Core Developers meeting on Dec. 15 discussed raising the network gas limit from 60 million to 80 million once the second BPO hard fork was implemented, which would increase the number of transactions and smart contract operations per block and potentially lower fees. Later in 2026 the Glamsterdam hard fork is slated to allow the gas limit to ratchet up to 200 million and introduce "perfect parallel processing" via Block Access Lists under EIP-7928, which seeks to transform Ethereum’s single-lane mode of transaction processing into a multi-lane highway to further increase throughput.

Key Topics

Crypto, Ethereum, Bpo Hard Fork, Glamsterdam Hard Fork, Rollups, Gas Limit