Zurich Battles Duplicate Images in Digital Archives

Zurich's public institutions are sitting on hundreds of thousands of duplicate digital images — redundant files that slow servers, inflate storage costs and, in some cases, have sent the wrong photograph into print or onto a government website. The problem is not new. But the scale of it, and the cost of correcting it, is only now becoming clear as the city and several of its anchor institutions undertake long-overdue database audits.

The timing matters. Several of Zurich's largest cultural and administrative bodies are mid-way through digital transformation programmes that were accelerated after the Covid years. ETH Zurich, whose library manages one of the largest research image repositories in the German-speaking world, began a structured deduplication review in early 2025. The Zentralbibliothek Zürich on Zähringerplatz, which holds digitised historical collections stretching back centuries, faces a version of the same challenge. When archives digitise at speed — often under grant deadlines or staffing pressure — the same physical photograph or illustration can be scanned more than once, filed under different metadata tags, and quietly duplicated across network drives.

How the Backlog Built Up

The roots of the problem trace to the early 2000s, when Swiss public institutions first began mass digitisation campaigns. Scanning was often done in siloed departments with no shared naming convention and no central registry. A photograph of the Grossmünster taken in 1952 might exist in one folder labelled by subject, another labelled by year, and a third imported from a legacy CD-ROM archive. Multiply that across two decades of piecemeal IT upgrades and the result is databases where, according to industry-standard estimates used by digital archivists across Europe, between 15 and 30 percent of image files are exact or near-exact duplicates.

The City of Zurich's own digital communications infrastructure — which serves departments spread from Stadthaus on Stadthausquai to the Amt für Städtebau offices in Wipkingen — expanded rapidly between 2010 and 2020 without a unified digital asset management system in place. Each department ran its own folder structures. When the city moved toward a centralised content management platform around 2021, staff importing legacy assets frequently pulled from multiple old drives, compounding existing duplication rather than resolving it.

Private institutions face the same pressures. The Kunsthaus Zürich, which completed a major expansion into the Chipperfield building in 2021, has a photography archive that spans both its original Heimplatz building and the new wing. Coordinating image rights, file versions and metadata across two buildings and multiple curatorial departments has produced its own duplication headaches, though the museum's digital team has been working to reconcile holdings since 2023.

The Cost of Doing Nothing

Storage is cheap by the gigabyte. Duplicate images are not just a storage problem, though. The real cost is human time: staff who pull the wrong version of an image, communications teams who publish an outdated photograph, and archivists who spend hours cross-referencing files that should have been consolidated years ago. Swiss IT consultancy estimates — not specific to any named client — typically put the administrative overhead of unmanaged duplication at several percent of a digital team's annual working hours.

Deduplication software exists and has improved considerably. Tools that use perceptual hashing can identify near-identical images even when file names differ, and cloud-based asset management platforms sold by vendors active in the Swiss market now include automated duplicate detection as a standard feature. The barrier is rarely technical. It is the unglamorous work of deciding which version of a duplicated file is canonical, updating metadata records, and retiring legacy folder structures that staff have relied on for years.

For institutions in Zurich navigating this now, the practical path forward involves three steps: a full audit of existing storage to establish the actual duplication rate, a governance decision on who owns the master record for any given image, and a migration to a system that prevents future duplication at the point of ingest. None of that is fast. But with several major Zurich institutions already committed to completing digital transformation reviews before 2028, the window for getting the foundations right is narrowing.