How Zurich's Digital Archives Ended Up Drowning in Duplicate Images — and What's Being Done About It

Zurich's municipal digital infrastructure is carrying a problem that has been building quietly since the early 2010s: thousands upon thousands of duplicate images lodged inside the city's public records systems, from heritage photo archives to planning department databases. The issue surfaced formally this spring when Stadt Zürich's IT department completed an internal audit — the results of which were presented to the Stadtrat in late May 2026 — flagging redundant image files as a primary driver of ballooning storage costs across civic platforms.

The timing matters. The city has been under sustained pressure to modernise public services while keeping administrative costs flat, a balancing act that has grown harder since the federal government's 2024 Digital Switzerland strategy pushed cantonal and municipal bodies to accelerate data consolidation. Duplicate images are not merely an aesthetic nuisance; they clog search indexes, return misleading results in public-facing portals, and force IT teams to manually verify records that should be retrievable in seconds.

A Long Chain of Well-Intentioned Uploads

The roots of the problem trace back to roughly 2012, when several departments — including the Stadtarchiv Zürich on Neumarkt and the Amt für Städtebau, which oversees planning records from its offices near Lindenhügel — began independent digitisation drives without a shared metadata standard. Each department chose its own file-naming convention. Images of the same building, the same event, or the same planning document were uploaded multiple times under different identifiers, with no automated deduplication layer sitting beneath the system.

The Stadtarchiv alone holds more than 2.3 million digitised items, a figure the archive has cited publicly in outreach materials. Even a duplication rate of two or three percent across a collection that size produces tens of thousands of redundant files. Multiply that across the Amt für Städtebau's construction permit imagery, the Stadtpolizei Zürich's public communications archive, and the records held at the Zentralbibliothek Zürich on Zähringerplatz, and the scale of the problem becomes clear.

Part of the difficulty is structural. Swiss direct democracy means that budget approvals for cross-departmental IT infrastructure require either executive sign-off from the Stadtrat or, for larger projects, a public referendum. Proposals for a unified city-wide document management platform were circulated internally as far back as 2018 but stalled over cost projections and jurisdictional questions about which department would own the master system.

What a Fix Actually Looks Like

The Stadtrat's May 2026 review pointed toward a two-phase remediation plan. The first phase, expected to run through the end of 2026, involves deploying perceptual hashing tools — software that identifies visually identical or near-identical images regardless of filename — across the three largest affected databases. The second phase, budgeted to begin in early 2027, would establish a shared ingest protocol so that new uploads from any participating department are automatically screened before being committed to storage.

The cost of cloud and on-premises storage has dropped significantly over the past decade, but at institutional scale the savings from deduplication are still meaningful. Industry benchmarks from comparable European municipal archives — including work done by the city of Vienna's MA 8 archive division — suggest that deduplication exercises routinely recover between 15 and 25 percent of active storage capacity. For Zurich, where the city's digital preservation budget has grown to absorb increasing volumes of born-digital material from departments across Kreis 1 through Kreis 12, even a conservative recovery figure represents real money redirected toward acquisition and access programs.

The practical upshot for residents and researchers is more direct than it might appear. Anyone who has tried to search the city's online planning portal for historical images of a Zürich neighbourhood — say, the transformation of Zürich-West around Hardbrücke over the past 30 years — has likely encountered duplicate thumbnails cluttering results pages. Once the hashing tools are deployed, those searches should return cleaner, faster results. The Zentralbibliothek has indicated it plans to update its public image search interface in line with the new backend changes, with a revised portal expected before the end of the first quarter of 2027.