Zurich Archives Push to Purge Thousands of Duplicate Images From City's Digital Records

Zurich's municipal administration confirmed this week that an ongoing project to identify and remove duplicate images from the city's digital archive systems has reached a critical phase, with preliminary checks showing tens of thousands of redundant files spread across multiple civic databases. The work, coordinated through the Stadtarchiv Zürich on Alfred-Escher-Strasse, is part of a broader effort to bring public record systems into compliance with updated cantonal data management standards that took effect on 1 January 2026.

The timing matters. Zurich has spent the past two years consolidating a patchwork of legacy IT systems inherited from district-level administrations, and image duplication has emerged as one of the most stubborn technical problems. A single photograph of a planning permit or infrastructure inspection can exist in four or five separate folders across different departments, driving up cloud storage costs and making it harder for civil servants and the public to locate authoritative source files.

What Happened This Week

On Tuesday, the Stadtarchiv confirmed it had begun a second-pass review using automated deduplication software piloted earlier this year. The tool, procured under a framework contract administered by the city's Informatik Zürich unit, flags files with identical pixel hashes and near-identical metadata before routing them to human reviewers for final sign-off. Staff at the archive's reading room on Alfred-Escher-Strasse said the first phase of the project, completed in spring, removed roughly 18,000 confirmed duplicate image files from the planning and building permit database alone — a figure the administration released in a brief internal status note seen this week.

ETH Zurich, operating its own separate digital infrastructure, announced Wednesday that the university's IT Services division had completed a parallel audit of image assets held in its research data repositories. The review covered material stored across the Hönggerberg campus data centre and the main Zentrum campus on Rämistrasse. ETH said the exercise was prompted partly by European Union-aligned open-access requirements and partly by the practicalities of managing decades of accumulated research imagery — satellite data, microscopy stills, and architectural surveys among them. The university did not release a final figure for duplicates removed but said the process was ongoing.

For ordinary Zurich residents, the most visible effect of poor image management has been in the city's public planning portal, which allows homeowners and developers in districts such as Wiedikon and Affoltern to check permit histories and neighbourhood surveys online. Duplicate images in those records have, in documented cases, caused version-control errors — showing an outdated site photograph as the most recent on file, which can complicate applications. The Stadtarchiv says it expects the current audit to be substantially complete by the end of the third quarter of 2026.

Costs and Broader Relevance

Storage is not cheap. Commercial cloud pricing benchmarks for institutional contracts in Switzerland currently run at roughly CHF 0.02 to CHF 0.05 per gigabyte per month, depending on redundancy tier. High-resolution municipal image files — many scanned at 400 dpi or above to meet archival standards — can run to several hundred megabytes each. Even modest deduplication gains across a large archive translate into measurable annual savings, though the Stadtarchiv declined to provide a projected figure before the audit concludes.

The issue has wider resonance in a city already grappling with data governance questions in the wake of the UBS-Credit Suisse merger, which forced Swiss financial regulators to develop new frameworks for managing vast combined datasets. While banking data and civic image archives are entirely separate domains, both cases illustrate the same underlying challenge: institutions that grew quickly now carry substantial digital dead weight that requires deliberate effort to clear.

Residents who believe a duplicate or incorrect image may be affecting their own planning or property records can contact the Stadtarchiv directly — appointments are handled through the city's online service portal. The archive has also indicated it will publish a summary report on the deduplication project findings once the third-quarter review is closed, which would give neighbourhood associations and planning professionals a clearer picture of which districts' records were most affected and what corrections have been applied.