Zurich's Digital Archive Reckoning: What Officials, Experts and Key Figures Are Saying About the Duplicate Image Crisis

Zurich's public institutions are sitting on a problem they can no longer quietly manage: tens of thousands of duplicate digital images clogging archive servers, inflating storage costs and complicating search systems that residents and researchers rely on daily. The issue has moved from an internal IT headache to a policy conversation involving archivists, data specialists and city administrators in recent months.

The pressure is real. Digital storage is not free, and for publicly funded bodies operating under Swiss federal data governance rules, the obligation to maintain clean, accessible records carries legal weight. The question now being asked in Zurich's administrative circles is not whether duplicates need to be removed, but how to do it without accidentally erasing irreplaceable historical material.

What the Experts Are Saying

At ETH Zurich, researchers in the university's Scientific IT Services division have been developing automated deduplication workflows for large image datasets since at least 2023. The approach involves perceptual hashing — a technique that identifies visually identical or near-identical images even when file names differ — combined with human review protocols before any deletion is confirmed. Specialists there have described the challenge as partly technical and partly organisational: the tools exist, but institutions need clear governance frameworks to use them responsibly.

The Stadtarchiv Zürich, located on Neumarkt in the Altstadt, holds one of the most extensive photographic collections in German-speaking Switzerland. Staff there have acknowledged in public presentations that the digitisation drives of the 2010s, while essential for preservation, produced significant file redundancy. A single historical photograph of, say, the Limmatquai in the 1950s might exist in four or five versions across different digitisation batches — each slightly different in resolution or colour profile, each occupying server space.

Digitisation specialists at the Zentralbibliothek Zürich on Zähringerplatz have raised a related concern: when duplicate images carry inconsistent metadata, catalogue searches return cluttered results that frustrate users. The library's digital collections, which include historical maps, photographs and printed ephemera, are accessed by researchers across Europe, making metadata quality a reputational as well as a practical issue.

The Costs and the Debate Over Deletion

Cloud and on-premises storage is not cheap at institutional scale. Enterprise-grade archival storage in Switzerland currently runs at roughly CHF 0.02 to CHF 0.05 per gigabyte per month depending on redundancy requirements, according to publicly available pricing from Swiss data centre operators. For an archive holding several hundred terabytes of image data, duplicate files can represent a meaningful share of that bill.

City officials have not yet announced a formal programme for duplicate removal across Zurich's public digital holdings. But within cantonal IT planning documents published in late 2025, digital asset rationalisation was listed among the priorities for the 2026–2028 planning cycle. The specific mechanism — whether centralised software, institution-by-institution audits, or a hybrid — remains under discussion.

The debate is not purely financial. Archivists argue that what looks like a duplicate to an algorithm may carry distinct evidentiary value: a slightly different crop, a handwritten annotation on the reverse, a different provenance chain. Any automated deletion programme, they say, needs a mandatory human verification step and a clear appeals process before files are removed from public collections.

For institutions in the Kreis 1 and Kreis 6 districts where many of Zurich's cultural memory organisations are clustered, the practical next step appears to be a pilot project. Sources familiar with the cantonal IT planning process say a working group involving the Stadtarchiv, the Zentralbibliothek and ETH Zurich's library services is expected to propose a coordinated deduplication framework by the end of 2026. Whether that proposal will require a budget allocation subject to cantonal council approval — and therefore potentially a public referendum under Swiss direct democracy rules — depends on its final cost estimate.

Residents with a stake in Zurich's cultural collections can follow developments through the Stadtarchiv's public programme at Neumarkt 4, where periodic information events on digital access are scheduled through the autumn.