How Zurich's Digital Archives Ended Up Full of the Same Image Twice — and What Comes Next

Zurich's public digital infrastructure has a clutter problem. Across municipal databases, the Stadtarchiv on Alfred-Escher-Strasse, and the cantonal records systems linked to the Staatsarchiv des Kantons Zürich on Winterthurerstrasse, tens of thousands of image files exist in duplicate — sometimes triplicate — the result of years of poorly coordinated digitisation drives, staff turnover, and incompatible software migrations. The issue is not new, but pressure to clean it up has reached a new pitch in 2026.

The immediate trigger is a city-wide data infrastructure review that the Stadtrat commissioned in early 2025 and whose preliminary findings circulated internally in the spring. The review, conducted across several departments including the Amt für Städtebau and the Präsidialdepartement's communications unit, found that redundant image files were driving measurable storage costs and degrading the reliability of public-facing search tools. Librarians and archivists who work with the collections describe spending significant portions of their working week manually resolving duplicate hits before they can answer a public query.

How the Backlog Built Up

The roots of the problem stretch back to the early 2010s. Zurich, like many European cities, embarked on an ambitious programme to digitise physical records — photographs, planning documents, maps — and push them into centralised repositories. The initiative was broadly successful. The Stadtarchiv alone moved tens of thousands of items online between 2012 and 2018. But the workflow was inconsistent. Different departments used different naming conventions. When systems were migrated from older platforms to newer ones, files were often imported wholesale rather than deduplicated first. Staff who left took institutional knowledge about which folders held originals and which held copies.

The problem compounded when the city upgraded its content management infrastructure around 2020 and again during the post-pandemic scramble to put more services online. Each migration created another layer of potential duplication. By the time a unified digital asset management policy was proposed in 2023 under the city's Smart City Zürich framework, the scale of the problem had grown large enough that a straightforward manual fix was no longer realistic.

ETH Zurich's computer science faculty has been a quiet partner in discussions about automated deduplication. Researchers there have worked on perceptual hashing — a technique that identifies visually identical or near-identical images even when their file names or metadata differ — and the city has been in exploratory talks about applying such tools to the municipal archive. No formal contract has been publicly announced.

The Cost and the Fix

Storage is not free. Commercial cloud storage at enterprise rates currently runs somewhere in the range of CHF 20 to CHF 40 per terabyte per month depending on tier and contract, and municipal systems that carry redundant files pay for capacity they do not need. For a city operating under perennial budget scrutiny — Zurich's 2025 municipal budget ran to roughly CHF 9.7 billion across all departments — even modest inefficiencies attract attention from the Gemeinderat's finance committee.

The practical consequences extend beyond cost. The Stadtarchiv's online search portal, which the public uses to access historical photographs of neighbourhoods from Wiedikon to Höngg, periodically surfaces the same image multiple times in a single results page. This is a minor irritation for casual users but a genuine problem for researchers, journalists, and heritage professionals who rely on the archive's metadata to distinguish originals from derivatives or later scans.

City administrators are now working through a phased remediation plan. The first phase, expected to run through the end of 2026, focuses on the Stadtarchiv's photographic collections, where duplication is most dense. The second phase will address planning and construction records held by the Amt für Städtebau. Automated tools will flag probable duplicates; trained staff will make final decisions on what to retain and what to retire to cold storage rather than delete outright.

For residents and researchers who use Zurich's digital public records, the practical advice is to note catalogue reference numbers rather than relying on image thumbnails — duplicate images frequently share visual appearance but carry different metadata, leading to confusion about provenance. The Stadtarchiv's reading room on Alfred-Escher-Strasse accepts appointments for in-person consultation for anyone whose research has been complicated by the current state of the online catalogue.