Crypto glossary
Shared and decentralized sequencers
Shared and decentralized sequencers replace a rollup's single operator with a network that orders transactions for one or several rollups at once.
A decentralized sequencer spreads the job of ordering a rollup's transactions across multiple independent operators, typically using a consensus protocol or a rotating leader. A shared sequencer goes further: one network orders transactions for several rollups at the same time, so a single block can include actions on different chains.
The goals are censorship resistance, uptime that does not depend on one company, and cross-rollup composability. If two rollups share a sequencer, a swap on one and a transfer on another can be guaranteed to land together, which isolated rollups cannot promise. Projects such as Espresso and several rollup stacks have built or tested such systems.
Adoption has been slower than the theory suggests. Rollup teams are reluctant to give up sequencer revenue and MEV, and shared ordering does not by itself guarantee atomic execution across chains, which also needs coordinated settlement. Some projects in this niche have pivoted or shut down, and based rollups offer a competing route through Ethereum's proposers.
Example
Two rollups plug into the same shared sequencer, letting a trader buy a token on one and sell it on the other with a guarantee that both orders are included in the same slot.