When did ETH Fusaka activate?

TLDR

Ethereum (ETH) activated the Fusaka upgrade on 3 Dec 2025 at 21:49 (UTC) on mainnet, marking its second major upgrade of the year Coindesk report.

1. Activation occurred at slot 13,164,544%%CKPROTECTED2%% on mainnet Coingape update.
2. Fusaka merges Osaka (execution) and Fulu (consensus) changes Yahoo Finance coverage.
3. PeerDAS enables up to 8x L2 data throughput and aims to lower L2 fees CryptoPotato brief.

Deep Dive

1. Exact Timing

The upgrade activated at 21:49 (UTC) on 3 Dec 2025, with core teams indicating a short finalization window after activation Coindesk report.

• Multiple outlets tracked the precise timing, with slot references and countdowns leading to mainnet activation Coingape update.

2. What Fusaka Is

Fusaka is a coordinated hard fork combining Osaka (execution layer) and Fulu (consensus layer) changes to improve scalability, security, and user experience Yahoo Finance coverage.

1. The centerpiece is PeerDAS (data availability sampling), allowing validators to check small slices of blob data instead of full blobs, cutting resource load and boosting throughput Coindesk report.
2. Ancillary EIPs refine gas rules and APIs, preparing the network for higher L2 volumes Coindesk report.

3. Why It Matters

PeerDAS and parameter changes aim to unlock up to 8x theoretical scalability for rollups and gradually reduce L2 fees, alongside a higher block gas limit near 60 million to expand capacity CryptoPotato brief and Binance Square note.

1. Expected fee reductions are cited in early coverage as L2s adopt PeerDAS and blob tuning flows through CryptoPotato brief.
2. The merge of execution and consensus improvements targets smoother ops for validators and better UX for wallets and apps Yahoo Finance coverage.

Conclusion

Fusaka activated on 3 Dec 2025 at 21:49 (UTC), aligning execution and consensus upgrades to scale Ethereums data capacity and improve L2 economics. The impact depends on how quickly rollups integrate PeerDAS and how network parameters are tuned in the coming weeks.