Zurich's Duplicate Image Problem: What Happens Next and the Key Decisions Ahead

Zurich's municipal digital infrastructure is carrying a problem that has been building quietly for years: thousands of duplicate images embedded across public planning portals, cantonal archive databases and the city's own communications platforms are now forcing a decision about how—and how fast—to clean house. The canton's digital governance office confirmed earlier this year that a formal audit of visual assets across departmental systems is underway, with preliminary findings expected before September.

The timing matters. Zurich is in the middle of an ambitious overhaul of its building permit and land-use planning systems, driven partly by pressure to accelerate housing approvals in a city where vacancy rates have hovered near record lows for three consecutive years. Redundant image files slow search indexes, inflate storage costs and—critically—introduce errors when outdated renderings of contested development sites appear alongside current ones. In a city where a single contested rezoning in Altstetten or Oerlikon can generate hundreds of official documents, a duplicate architectural image attached to the wrong file version is not a trivial bureaucratic nuisance.

Where the Backlog Is Worst

Two institutions are at the centre of the problem. The Stadtarchiv Zürich, based at Neumarkt 4 in the Altstadt, holds tens of thousands of digitised historical photographs, many of which were scanned multiple times during successive digitisation drives between 2010 and 2022. Staff there have been working with a cataloguing framework inherited from pre-merger workflows that pre-date the current canton-wide data strategy. The second pressure point is the online platform maintained by Amt für Städtebau, the city's urban development office, where project visualisations submitted by developers are stored. Because the submission portal does not automatically flag pixel-identical or near-identical files, duplicate renderings of the same Hochhaus proposal or Quartierplan revision accumulate without triggering any alert.

ETH Zurich's Chair of Cognitive Computing, whose teams have consulted on similar deduplication challenges for European municipal clients, has published research suggesting that automated perceptual hashing—a technique that identifies visually similar images even when file names differ—can reduce manual review burdens by up to 70 percent compared with human-only audits. That figure has circulated inside cantonal IT circles as a benchmark for what a procurement of deduplication software should be expected to deliver.

Storage costs are not theoretical. Canton Zurich's 2025 budget allocated roughly CHF 4.2 million to general digital infrastructure maintenance across civic departments, a figure that includes server capacity for document and media assets. Independent IT consultants familiar with Swiss public sector contracts estimate that poorly managed image duplication can inflate active storage demand by 15 to 30 percent in large municipal archives—a range that, applied to Zurich's known holdings, points to a potentially significant waste of public funds.

The Decisions Coming This Autumn

Three choices will define what comes next. First, the canton must decide whether to run a centralised deduplication process managed from a single IT authority, or to push the work out to individual departments—a devolved model that is faster to launch but historically produces inconsistent results across the Stadtarchiv, Amt für Städtebau and the communications offices at Stadthaus Zürich. Second, officials will need to settle on a retention policy: when two versions of the same image exist, which one is canonical, and who has sign-off authority? For historical photographs of places like Langstrasse or the Limmatquai, that is also a question about cultural heritage stewardship, not just data hygiene. Third, and most politically sensitive, is whether the cleaned archive will be made fully accessible through the city's Open Government Data portal at data.stadt-zuerich.ch, where over 800 datasets are already published.

Public consultation on the digital governance framework closes on 30 September. Residents and civic organisations have until that date to submit written input through the canton's standard Vernehmlassung process. What the autumn brings will depend on whether the political will exists to fund a proper procurement rather than a piecemeal fix—and whether departments that have jealously guarded their own image libraries are prepared to cede control to a unified system. Neither outcome is guaranteed.