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

Zurich's municipal digital infrastructure is carrying a burden that has been accumulating quietly for more than a decade: tens of thousands of duplicate image files scattered across city-run archives, slowing search systems and inflating storage costs at a time when the city is spending heavily on digital modernisation. The problem, now formally acknowledged by Stadt Zürich's digital governance office, did not arrive overnight.

The roots go back to roughly 2012 and 2013, when multiple city departments launched their own digitisation drives with little coordination between them. The Stadtarchiv Zürich on Neumarkt, the urban planning office at Amtshaus IV on Fraumünsterstrasse, and the communications department each contracted separately with different vendors, using incompatible metadata standards and no shared deduplication protocol. Files captured once were often re-scanned, re-uploaded and re-tagged under different naming conventions. A single photograph of the Lindenhügel or the tram network on Bahnhofstrasse might exist in four or five versions across as many servers.

Why the Problem Compounded Over Time

The UBS–Credit Suisse merger aftermath created an indirect pressure on the city's own institutional behaviour. As Zurich's financial sector consolidated aggressively between 2023 and 2025, city planners and digital administrators found themselves in repeated budget reviews, and longer-term infrastructure projects — including archive rationalisation — were deferred. Short-term contracts were renewed rather than replaced with unified systems. Storage kept expanding. The Stadtwerk Zürich data centres in Altstetten absorbed the overflow.

ETH Zurich's Chair of Information Science published a working paper in March 2025 estimating that Swiss public-sector digital archives broadly carry a duplication rate of between 18 and 24 percent across image files, a figure that aligns with internal assessments that city officials have since referenced in budget documents seen by this newspaper. For a city the size of Zurich — whose municipal digital budget for 2026 was set at approximately CHF 47 million — that redundancy translates into wasted licensed storage, slower retrieval for journalists, planners and residents making public records requests, and compounded errors when outdated image versions are pulled instead of current ones.

The housing shortage has made the duplication issue more than academic. Wohnungsnot pressure on Zurich's Kreise 4 and 5 has driven a surge in planning applications and neighbourhood consultation processes, many of which rely on geo-tagged municipal images. When planning staff pull duplicate or outdated aerial photographs of the Langstrasse quarter or Zürich-West development zones, the downstream errors can delay approval timelines. A single misidentified building footprint — caused by an older image overriding a newer scan — held up a 34-unit residential project on Hohlstrasse for nearly three months in late 2024, according to planning documents filed with the city.

The Cleanup Effort Taking Shape Now

Stadt Zürich launched a formal duplicate-image replacement programme in January 2026, managed through the Departement der Industriellen Betriebe in coordination with the Office of Digital Transformation on Walchestrasse. The initiative involves automated hash-matching software to identify exact and near-duplicate files, followed by manual review for images flagged as contextually significant. Archivists at the Stadtarchiv are working through a backlog the programme administrators have described in public budget filings as covering approximately 2.3 million indexed image assets.

The timeline is not short. Phase one, covering records from before 2018, is scheduled for completion by the end of 2026. Phase two, addressing more recent files, runs through 2027. Residents and organisations that rely on public image databases — including architectural firms working near Zürichhorn and community groups in Höngg — have been advised to submit fresh data requests rather than relying on cached results during the transition period.

For ordinary Zurichers, the practical effect will be most visible in the city's online Stadtplan portal, which draws on the same image repositories. City administrators have indicated that the portal will begin returning cleaner, faster results as consolidated image sets replace the current fragmented ones. The work is unglamorous, expensive and overdue — but the alternative, officials have noted in budget presentations, is a digital infrastructure increasingly at odds with a city that expects its services to function precisely.