TLDR
Ethereum (ETH) Fusaka went live on mainnet on 3 Dec 2025 at 21:49 (UTC), confirmed by multiple official and reputable sources.
- Activation time was 21:49 (UTC) on 3 Dec 2025 per a node operator notice and community confirmations here.
- Official posts state Fusaka went live December 3 and 9:49 p.m. UTC on mainnet here and here.
Deep Dive
1. Exact Time
The most precise timestamp cited is 21:49 (UTC) on 3 Dec 2025, as communicated to node operators supporting the upgrade here. Multiple public posts echoed the same day and timing, including the Ethereum account noting went live December 3 %%CKPROTECTED1%% and a 9:49 p.m. UTC confirmation here.
- Media recaps place the go?live at roughly 21:49 (UTC), aligning with mainnet activation reports here.
- Roundups and calendars listed 34 Dec windows, but the definitive activation was the evening of 3 Dec (UTC) here.
If you needed the exact cutover moment for node operations or time?boxed analytics, use 3 Dec 2025, 21:49 (UTC) as the mainnet activation reference.
2. Why It Matters
Fusaka combines the Fulu (consensus) and Osaka (execution) upgrades to scale Ethereum without compromising security. Key features include PeerDAS for data availability sampling, an L1 gas limit increase to 60 million, and UX improvements such as the R1 curve and pre?confirmations here and here.
- PeerDAS can unlock around 8x data throughput for rollups, reducing costs and improving performance here.
- The gas limit increase supports higher transaction capacity and lower fees as rollups adapt here.
Over the coming weeks, expect L2 fees to trend lower and throughput to improve as rollups adopt Fusaka features, benefiting users, apps, and validators.
Conclusion
Fusaka went live on 3 Dec 2025 at 21:49 (UTC), marking a significant scaling step for Ethereum that improves rollup data capacity and network throughput. The upgrade sets the stage for lower L2 costs and better user experience as adoption spreads across the ecosystem.
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