Zurich's Digital Archives Are Full of the Same Photo Twice — Experts Want That Fixed

Zurich's municipal digital infrastructure is carrying a significant weight of redundant visual data. Stadtarchiv Zürich, the city's official records office on Alfred-Escher-Strasse, has acknowledged that duplicate image files account for a measurable share of its storage burden — a problem that has grown steadily since the mass digitisation drives of the early 2010s accelerated the intake of scanned documents, photographs and urban-planning materials. The archive declined to provide a precise figure, but specialists familiar with the sector place industry-wide duplication rates in large institutional collections at between 15 and 30 percent of total file volume.

The issue has moved from a back-office nuisance to a policy conversation. Switzerland's federal data-management guidelines, last updated in 2023 under the Bundesgesetz über das Archivwesen, require public bodies to maintain clean, retrievable records — and storing dozens of identical or near-identical images of, say, the Lindenhügel or a construction permit for a Zürich-West development block is increasingly seen as non-compliance by another name. The urgency is sharpened by the housing shortage: the Wohnungsnot crisis means planning documents, including site photographs, are being generated and deposited into shared municipal systems faster than quality controls can keep pace.

What the Specialists Are Saying

ETH Zurich's Institute for Information Security has been studying automated deduplication pipelines as part of a broader research strand on public-sector data governance. Researchers there have presented findings suggesting that perceptual hashing — a technique that identifies visually similar images even when file names or metadata differ — can reduce duplicate rates in institutional collections by more than half without human review of every file. The institute has not yet published a final report, but presentations at the Swiss Digital Days conference in autumn 2025 drew interest from cantonal IT offices.

Fachstelle Digitalisierung, the city of Zurich's own digitalisation unit based in the Stadthaus on Stadthausquai, has been piloting a deduplication workflow since January 2026 across a subset of building-permit image archives. The pilot covers records from the Kreis 4 and Kreis 5 districts — both areas of intense redevelopment activity — and is expected to run through September 2026 before results are formally reviewed. Staff involved in the project describe the core challenge not as technology but as governance: who has authority to declare an image a duplicate, and what happens to the discarded copy?

That governance question is where consensus breaks down. Stadtarchiv archivists argue that deletion requires a documented retention decision under cantonal law. Software vendors pushing AI-assisted tools — several have approached the city since the pilot launched — argue that near-duplicate images with no unique metadata can safely be collapsed into a single master file immediately. Librarians at Zentralbibliothek Zürich on Zähringerplatz, which manages its own photographic collections separately, have quietly aligned with the archivists' more cautious position.

The Cost of Doing Nothing

Storage is not free. Zurich's municipal IT budget, published in the Stadtrat's 2025 Rechnung, allocated 4.2 million francs to digital infrastructure maintenance across all departments — a line that has grown year on year. Independent IT consultants who work with Swiss public bodies estimate that uncontrolled image duplication adds between 8 and 12 percent to storage costs over a five-year cycle, though those figures are not specific to Zurich and have not been independently audited for this context.

There is also a practical access problem. Journalists, urban planners and residents using the city's online portal, Zürich Maps, have complained that searches for historical images of specific sites — Escher-Wyss-Platz is one frequently cited example — return multiple identical results, cluttering searches and slowing downloads.

The Fachstelle Digitalisierung pilot is scheduled to deliver a first interim report to the Stadtrat in October 2026. If the Kreis 4 and Kreis 5 results are positive, a city-wide rollout across all departments could follow in 2027, potentially covering hundreds of thousands of image files. For now, archivists, technology researchers and policy officials agree on the diagnosis. The prescription, and who writes it, is still being argued over.