Strata is an open-source tool for reading the archived web at scale. It draws every address in a domain, collection or web sphere as a layer on a shared timeline, from its first archived capture to its last. Each layer is marked with the web archives that witnessed it.

Web archives are built to be consulted one page at a time, and that serves the historian of a single document well. It serves poorly anyone who wants to know how the web itself has changed: how long websites live, which disappear unnoticed, and whose record survives. Strata enables scalable reading, moving between the individual capture and the pattern formed by thousands. Setting independent web archives side by side shows where they agree, where they differ, and which appraisal decisions, rarely seen, have shaped the record we inherit. The aggregate never displaces the evidence: every pattern leads back to the capture that produced it.