Crypto glossary
Sovereign rollup
A sovereign rollup posts its transaction data to a data availability layer but decides its valid chain through its own nodes, with no settlement contract on L1.
A typical rollup on Ethereum has a smart contract there that verifies proofs and decides the canonical state. A sovereign rollup has no such contract. It publishes its blocks to a data availability layer such as Celestia, Avail or even Bitcoin, and its own full and light nodes download that data and apply the rollup's rules to decide which chain is valid, much like an independent L1.
The appeal is independence. The community can upgrade or fork the rollup through social consensus, as with any sovereign chain, without needing permission from a contract on another network, while still outsourcing block ordering and data availability. The idea became prominent with the modular blockchain movement and the launch of dedicated DA layers.
The cost is that there is no trust-minimised bridge built in: since the DA layer does not verify state, moving assets to and from other chains needs separate bridges with their own assumptions. Liquidity and tooling are thinner than in Ethereum's rollup ecosystem, and the label is sometimes applied loosely to chains that are closer to standalone L1s.
Example
A team launches a sovereign rollup that posts data to Celestia; when it later needs a protocol change, node operators simply upgrade their software, with no L1 contract to migrate.