Storage Buckets gives sites the ability to organize on-device data into separate "buckets", allowing user agents to evict the grouped data independently of that which is in other buckets, and enabling sites to ergonomically manage semantically related data. Each storage bucket can contain data associated with established storage APIs such as IndexedDB and CacheStorage.
Currently, when there is storage pressure or the user has a low disk device, sites have no control over how their storage gets evicted during browser storage eviction. Today, there is only a binary choice to either persist or delete all the data stored by a site. Storage Buckets API will allow sites to partition data, manage quota, and set eviction prioritization so sites can specify which bucket to remove first during browser storage eviction.
Explainers: https://github.com/WICG/storage-buckets/blob/main/explainer.md