Zurich's Digital Archives Are Littered With Duplicate Images — Here's What Officials and Experts Want to Do About It

Zurich's public institutions are sitting on a growing problem buried inside their own servers: thousands of duplicate images cluttering digital archives, inflating storage costs, and undermining the integrity of datasets used for everything from urban planning to academic research. The issue has moved from an IT footnote to a governance concern, and the people responsible for fixing it are now speaking with unusual urgency.

The timing matters. Across Switzerland, the post-Credit Suisse regulatory atmosphere has sharpened scrutiny of how institutions manage and verify their digital assets. At the same time, ETH Zurich — consistently ranked among the world's top ten universities for engineering and technology — has been expanding its open-access data platforms, where image duplication creates real problems for reproducibility in published research. Sloppy archives are not merely an aesthetic failing; they carry reputational and legal weight.

What the Specialists Are Actually Saying

Experts working with Zurich's municipal digitisation office and with research data management units at ETH Zurich have been pushing for what they describe as systematic deduplication protocols — automated processes that scan repositories, flag identical or near-identical image files using hash-matching algorithms, and route them for human review before deletion. The conversation has been building since at least early 2025, when the city's IT directorate on Beatenplatz began auditing the storage footprint of digitised planning documents, many of which contained the same aerial photographs submitted multiple times across different project files.

Practitioners in the field point to two distinct failure modes. The first is accidental duplication: the same scan uploaded twice, or an image attached to multiple submissions without anyone noticing. The second is more troubling — intentional re-use of images across separate submissions to regulators or funding bodies, which in research contexts can constitute a form of data manipulation. The two problems require different responses, and conflating them has slowed progress.

At the Stadtarchiv Zürich on Neumarkt, archivists have been working since January 2026 on a pilot project that applies perceptual hashing to its photographic holdings — a technique that catches near-duplicate images even when file names, metadata, or minor edits differ. The archive holds more than 1.3 million digitised photographs, according to figures the institution has published on its public-facing website, and staff there have acknowledged that the initial audit found duplication rates higher than anticipated in collections ingested between 2018 and 2022.

The University of Zurich's library services directorate, based near the Rämistrasse campus, has separately been coordinating with Swiss National Science Foundation guidelines issued in 2025 requiring research data deposited in funded projects to meet minimum quality and uniqueness standards. Librarians there have been vocal in workshops this spring that the tools exist — the will to enforce their use consistently has lagged behind.

The Cost Question and What Comes Next

Storage is not free. Cloud infrastructure costs for Swiss public institutions have climbed in line with broader European trends, and one widely cited estimate from a 2024 Digitale Verwaltung Schweiz working paper suggested that avoidable data redundancy accounts for between eight and fifteen percent of public sector cloud expenditure across the confederation. Applied to Zurich's own digital infrastructure budget, that range represents a meaningful sum.

The practical path forward, as described by data governance specialists who have been presenting at forums including the annual Swiss Informatics Society conference, runs through three stages: standardise deduplication tooling across cantonal and municipal platforms; train staff who upload and manage digital assets; and build audit trails so that deleted duplicates can be traced if questions arise later.

For Zurich residents and institutions that interact with city databases — submitting planning applications through the online Stadtentwicklung portal, for instance, or depositing research outputs — the immediate advice from those closest to the review process is straightforward: submit files with consistent naming conventions, avoid repackaging the same image under different labels, and check submission guidelines before uploading. The systems being built to catch errors will not replace careful practice on the front end.

A formal set of cantonal-level recommendations is expected before the end of the third quarter of 2026, according to the Digitale Verwaltung Schweiz work programme published this year. Whether institutions move quickly once those guidelines land is the question professionals in Zurich's archival and research communities are already debating.