Zurich's Digital Archives Have a Duplicate Image Problem — and Officials Are Starting to Talk About It

Zurich's municipal digital infrastructure is sitting on a growing pile of duplicated image files — and the people responsible for managing those systems are no longer keeping quiet about it. Across cantonal archives, university repositories and city planning databases, the accumulation of redundant visual data has become a measurable administrative headache that several institutions are now actively working to address.

The issue has sharpened focus recently because of concurrent pressures: the city's ongoing Wohnungsnot housing crisis has pushed planning departments to digitise thousands of building survey photographs at speed, while ETH Zurich's continued expansion of its research data infrastructure has forced a harder look at what exactly is being stored — and how many times. The result is a patchwork of overlapping image libraries that specialists say costs both money and operational clarity.

What the Experts Are Saying

Professionals working in digital asset management at institutions along Rämistrasse and at the Stadtarchiv Zürich near Neumarkt have described the core problem in consistent terms: images uploaded through multiple workflows — by different departments, contractors or research teams — often arrive without standardised metadata, making automated deduplication unreliable. Without a shared hashing protocol or a central registry, the same photograph can exist under four different filenames across two different servers.

Staff at the Stadtarchiv, which holds records covering the city's documented history from the medieval period forward, have noted in public presentations that image file management was flagged as a priority in the archive's 2024-2026 digitisation strategy. The strategy set a target of reducing redundant file storage by consolidating legacy image batches ahead of a planned system migration. ETH Zurich's IT Services division has separately acknowledged that research group repositories — particularly in the architecture and urban planning faculties, which generate high volumes of photographic documentation — require periodic deduplication audits to remain within allocated storage quotas.

The Swiss Federal Archives in Bern have also engaged with the question at a national level. Their guidance documents on digital preservation standards, last updated in 2023, specify checksum-based verification as best practice for identifying duplicate files within long-term archival systems. Institutions in Zurich that have adopted those federal recommendations report fewer redundancy errors during ingestion, though implementation across smaller municipal departments remains uneven.

Cost and Scale of the Problem

Storage is not free. Enterprise-grade archival storage in Switzerland currently runs at roughly CHF 0.02 to CHF 0.05 per gigabyte per month depending on redundancy tier and provider — figures that compound quickly when an institution is unknowingly maintaining three or four copies of the same high-resolution scan. A single digitisation project covering one district's building permits can produce upward of 50,000 images; if even 15 percent of those are duplicates, the wasted storage runs into hundreds of gigabytes before anyone notices.

The Zurich cantonal IT office, the Amt für Informatik, has been running a pilot programme since early 2025 testing perceptual hashing tools — software that identifies near-identical images even when file names or metadata differ — across two pilot departments. Results from that pilot have not yet been published publicly, but the programme is understood to be informing a broader cantonal data governance review expected to conclude by the end of 2026.

For institutions not yet enrolled in a formal deduplication programme, specialists recommend three immediate steps: establishing a single point of image ingestion with automatic hash-checking at upload, enforcing a naming convention tied to creation date and source department, and scheduling quarterly audits of any folder structure older than 18 months. The Bibliothek am Zähringerplatz, which handles community digitisation requests for local historical societies, has already implemented a modest version of this approach using open-source tools since January 2026.

The broader conversation is unlikely to resolve itself before the cantonal review lands. But the direction of travel is clear — Zurich's data managers are done treating duplicate images as a minor inconvenience. At the scale these institutions now operate, it is a budget issue with a paper trail.