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What is a shared sequencer?
A shared sequencer is a single sequencing network that orders transactions for several rollups at once, instead of each rollup running its own sequencer. Because it sees their transactions together, it can arrange for linked transactions on two rollups to be handled together or not at all.
What it means for you
A shared sequencer is a point every connected rollup depends on: if it censors, fails or reorders transactions, all of them feel it. Its main promise to users, acting on one rollup and another in one step, depends on the strength of the guarantee: being included in the same batch is not the same as both transactions succeeding.
How it works
Rollups currently rely on a centralized sequencer to order transactions. Shared sequencing processes the transactions of multiple rollups together. One research design forms the shared sequencer by aggregating each rollup's sequencer and selecting a leader; it aims for synchronous atomic execution, where transactions on different rollups all succeed or all fail, which needs more than ordering: an executor runs the agreed order and a verification layer checks the outcome. A separate study modelling arbitrage between two pools found that atomic execution does not always raise profits and can lead to losses.
Sources: Cross-rollup synchronous atomic execution (Ko and Ju, Ethereum Research), Atomic Execution is Not Enough for Arbitrage Profit Extraction in Shared Sequencers (arXiv:2410.11552), SoK: Decentralized Sequencers for Rollups (arXiv:2310.03616) · checked 4 October 2026
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