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

Zurich's municipal digital infrastructure is sitting on a problem that has been quietly growing for years. Thousands of duplicate images — building permits, planning documents, historical photographs, public health records — have accumulated across city servers, creating storage bloat, retrieval failures, and a compliance headache that cantonal archivists at the Stadtarchiv Zürich can no longer defer. The question now is not whether to act, but how fast, and who pays.

The timing matters. Switzerland's revised federal Data Protection Act, which came into force in September 2023, imposed stricter obligations on public bodies handling personal data embedded in visual records — and duplicate files multiply the exposure. For Zurich, a city that has made digital government a centrepiece of its 2030 Smart City strategy, tolerating redundant archives is increasingly difficult to justify politically or legally.

What the Backlog Actually Looks Like

The Stadtarchiv, housed near the Rathaus on Neumarkt, manages records spanning centuries, but the digital duplication issue is largely a product of the last decade. Multiple city departments — Tiefbauamt, Stadtentwicklung, Gesundheitsdepartement — operate semi-autonomous storage systems that do not communicate cleanly with each other. When a planning image is submitted, revised, and resubmitted across departments, copies proliferate with no automatic deduplication layer in place.

ETH Zurich's Computational Science department has studied similar data redundancy challenges in European municipal contexts and published findings suggesting that medium-sized city administrations routinely carry between 15 and 30 percent duplicate digital assets across fragmented departmental systems — a figure that carries real cost implications when multiplied across petabyte-scale storage contracts. Zurich's own storage procurement through city IT provider OIZ (Organisation und Informatik) runs on rolling multi-year contracts, and the next renewal window opens in early 2027, giving administrators roughly six months to define what a cleaned, rationalised archive should look like before new terms are locked in.

The housing crisis adds a specific urgency. Baubewilligungen — building permits — are among the most duplicated document classes in the city system, partly because the Wohnungsnot pressure has driven a surge in applications across Zürich Wiedikon, Altstetten, and Schwamendingen since 2022. Each contested or revised application can spawn multiple image attachments across the Stadtentwicklung Zürich review chain, with no single point of deduplication.

The Decisions That Cannot Wait

Three choices now sit on the desk of city IT leadership. First, whether to run a one-time manual audit or invest in automated hash-based deduplication software — a tool that compares file fingerprints rather than filenames, catching renamed or slightly reformatted duplicates that manual checks miss. Second, whether deduplication is handled centrally by OIZ or devolved to individual Departemente, each of which has resisted centralisation in previous IT consolidation rounds. Third, how to handle images that contain personal data — faces, addresses, health records — that cannot simply be deleted without a formal retention review under cantonal Archivgesetz provisions.

The Stadtrat's digital governance committee is expected to receive a preliminary options report before the summer recess ends in late August. Budget implications are real: comparable deduplication projects in comparable European administrations — Geneva ran a partial exercise across its cantonal document system in 2024 — have cost between CHF 400,000 and CHF 1.2 million depending on scope and whether legacy migration is included.

For residents and businesses filing planning applications through the city's online portal on Amtshaus IV at Bahnhofquai, the practical effect of inaction is slower document retrieval and occasional system errors when search functions return redundant file hits. For the archivists at Neumarkt, it is a question of institutional credibility. A city that positions itself as a global leader in civic technology — ETH Zurich consistently ranks in the world's top ten research universities — cannot indefinitely maintain a back-end that contradicts that reputation. The decisions made before the OIZ contract renewal in 2027 will set the terms for at least the following five years.