Zurich Takes a Methodical Approach to Duplicate Image Replacement — and Other Cities Are Watching

Zurich's city administration confirmed this spring that a structured audit of its public-facing digital archives — spanning municipal permit portals, transport authority image libraries, and the city's official tourism platforms — had uncovered more than 4,200 duplicate image files consuming unnecessary server bandwidth and creating legal grey zones around licensing. The cleanup effort, running since February 2026 under the Stadt Zürich Departement der Stadtentwicklung, is roughly 60 percent complete.

The timing is not accidental. Cities across Europe have faced mounting pressure to rationalise their digital asset management as data protection obligations under Switzerland's revised Federal Act on Data Protection, which came into full force in September 2023, push public bodies to audit not just personal data but all stored digital content. Duplicate images — particularly those showing identifiable locations, faces in crowd shots, or commercially sensitive architectural details — can create compliance headaches that city legal teams have only recently started taking seriously.

Zurich's approach differs from what Amsterdam and Vienna have pursued. Amsterdam's Gemeentearchief began a comparable deduplication exercise in 2024 but contracted it out to a private vendor, a decision that drew criticism from municipal councillors concerned about data sovereignty. Vienna's Stadtarchiv went the opposite route, building an in-house tool that took nearly three years to deploy and still lacks automated hash-matching for older TIFF-format files. Zurich sat somewhere between those two poles, deploying an open-source perceptual hashing framework that the city's own IT department at Stadthaus Zürich adapted and tested in-house before rolling it out across departments.

Local Institutions Leading the Practical Work

Two organisations have been central to the project. ETH Zurich's Data and Service Center for the Humanities, based on Rämistrasse, provided technical consultation during the audit's design phase, and the Zentralbibliothek Zürich on Zähringerplatz contributed archival standards expertise drawn from its own digitisation work on historical newspaper collections. Neither institution is running the city's database directly — that responsibility sits with municipal IT — but the collaboration reflects a pattern Zurich has used before: pulling in research infrastructure without outsourcing the accountability.

The practical stakes are visible in the Langstrasse and Kreis 4 streetscape photography that appeared across at least three separate city portals in conflicting versions — some watermarked, some not, some carrying different Creative Commons designations. When a private developer cited one of those conflicting images in a planning dispute last year near Bäckeranlage park, the documentation problem cost the city's planning office six additional weeks in verification. That kind of delay, multiplied across dozens of projects, adds up fast in a city where the housing shortage is already slowing construction timelines.

How Zurich Compares Globally

By the numbers, Zurich's 4,200-file duplicate backlog sounds modest. Singapore's Urban Redevelopment Authority publicly disclosed a far larger problem in late 2024 — roughly 38,000 redundant image assets across its public development portal — though Singapore benefits from a more centralised government IT structure that made bulk deletion operationally simpler. London's various borough councils, lacking any unified image repository, have no equivalent audit at all; each of the 32 boroughs manages assets independently, which digital governance researchers at University College London described in a March 2026 working paper as an emerging compliance liability.

Zurich spent approximately CHF 180,000 on the audit and remediation through the first half of 2026, according to budget documents reviewed by The Daily Zurich from the city's spring supplementary estimates. That figure includes staff time but excludes the ETH consultation, which was provided under an existing research partnership framework.

The audit is scheduled to finish by September 2026. Once it does, the city plans to publish its adapted open-source tool under a public licence, making it available to other Swiss municipalities through the Verein eCH, the Swiss e-government standards body. For smaller cantons with fewer IT resources — Glarus and Appenzell Innerrhoden have both expressed informal interest, according to city documents — a ready-made tool calibrated to Swiss data protection standards would fill a gap that no commercial vendor has yet bothered to address at that scale.