TLDR
Ethereums Fusaka mainnet upgrade is scheduled for December 3, 2025, with activation around 21:49 (UTC) at block 13,164,544 per a developer timeline update (crypto news report).
- Final tests completed on Holesky, Sepolia, and Hoodi, with Hoodi on October 29 (network update).
- Cointelegraphs roadmap explainer also confirms the December 3 activation date (explainer).
- Core feature is PeerDAS to scale L2 data throughput and reduce validator load (explainer).
Deep Dive
1. Exact Timing
The Fusaka hard fork for Ethereum (ETH) is slated for December 3, 2025, with activation targeted around 21:49 (UTC) at block 13,164,544. That timestamp and slot were set after coordination calls and testnet sign-offs (crypto news report).
This date is echoed across multiple coverage pieces and technical summaries focused on the upgrades content as well as rollout specifics (roadmap explainer).
2. Readiness
Core teams completed test runs on Holesky, Sepolia, and Hoodi, with Hoodi marked as the final stage on October 29 before mainnet scheduling (network update).
Separately, validators raised the block gas limit to 60 million ahead of Fusaka, indicating network readiness and capacity work leading into the upgrade (coverage).
The date is firm and supported by recent testnet and capacity changes. If you plan around the upgrade, use UTC for timing and expect phased post-upgrade parameter increases.
3. Why It Matters
Fusaka introduces PeerDAS (peer data availability sampling), enabling validators to verify data by sampling rather than downloading full blobs. This reduces bandwidth/storage while unlocking higher L2 data throughput (explainer).
The upgrade also sets the stage for Blob Parameter Only forks to incrementally raise blob capacity, plus fee and limit tweaks that improve predictability and throughput for L2s (explainer).
For users and builders, watch L2 fees and batch costs after Dec 3. Lower data costs and more capacity could improve UX and broaden activity on rollups.
Conclusion
Fusakas mainnet activation on December 3, 2025 (UTC) is a confirmed milestone that targets L2 scalability and validator efficiency. The combination of PeerDAS and incremental blob capacity increases could meaningfully reduce data costs and improve throughput, positioning ETH for stronger rollup economics and user experience as follow-on parameter raises roll out.
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