How Zurich's Digital Archives Ended Up Drowning in Duplicate Images — and What Comes Next

Zurich's public institutions are sitting on millions of duplicate digital images — the accumulated residue of at least a dozen separate digitisation drives launched between 2012 and 2024 — and the city's archivists, museum technologists, and IT managers are only now grappling seriously with the scale of the problem.

The issue matters right now because the City of Zurich's digitisation strategy is entering a consolidation phase. The municipal administration published a framework document in late 2024 calling for rationalisation of digital asset storage across departments, and institutions from the Stadtarchiv on Alfred-Escher-Strasse to the Zentralbibliothek at Zähringerplatz are being asked to audit what they actually hold. That audit process has surfaced a problem that insiders had quietly acknowledged for years: the same image files, often in multiple resolutions and file formats, exist in parallel across separate servers, cloud buckets, and legacy tape backups.

How did it get this way? The trajectory is not complicated, even if the technical mess is.

A Decade of Fragmented Digitisation

Between roughly 2012 and 2020, Swiss cultural institutions benefited from a run of federal and cantonal funding tranches aimed at digitising historical collections. The Swiss National Science Foundation backed several ETH Zurich-linked research projects that produced high-resolution image datasets. The city's own museums — among them the Kunsthaus Zürich on Heimplatz, which completed a major archive digitisation as part of its 2021 extension project — each developed their own workflows, their own metadata schemas, and critically, their own storage infrastructure.

Nobody was coordinating at the city level. The Stadtarchiv ran its own digitisation pipeline. The Museen der Stadt Zürich operated separately. The Zentralbibliothek, which holds cantonal and municipal collections jointly, developed its e-rara and e-manuscripta pipelines in collaboration with other Swiss libraries — producing yet another parallel repository. When projects concluded, the deliverables — often tens of thousands of TIFF files per collection — were deposited into whatever server environment the project had used, and rarely pruned afterwards.

By 2023, storage costs had become a measurable budget line. Switzerland's commercial cloud storage market is not cheap: enterprise-tier object storage from Swiss providers typically runs at considerably higher per-gigabyte rates than comparable services from US hyperscalers, largely because of Swiss data residency requirements and energy costs. Institutions that had quietly accepted redundant storage as a technical inconvenience began noticing it as a financial one.

The Reckoning Arrives

The trigger for the current push was partly the UBS absorption of Credit Suisse's technology infrastructure after the March 2023 emergency merger — an event that had nothing directly to do with cultural archives, but which put Swiss data governance and digital consolidation firmly on the agenda of public administrators watching the private sector scramble. Municipal IT departments drew their own lessons about what happens when parallel systems are allowed to proliferate without oversight.

ETH Zurich's IT Services division has been working since 2024 on image-deduplication tooling as part of a broader research data management initiative, applying perceptual hashing and file-fingerprinting techniques to identify near-duplicate images in large scientific datasets. The methods being tested there are directly applicable to the cultural heritage problem, and at least two Zurich city institutions have been in contact with the ETH team about potential collaboration, according to publicly available meeting minutes from the Stadtarchiv advisory board.

The practical path forward involves several steps. First, institutions must complete their storage audits — a process that will run through the end of 2026 under the current municipal timetable. Second, a common deduplication standard needs to be agreed upon, so that a photograph of, say, the Lindenhügel held in three separate archives does not get deleted from two of them without a record of which version is canonical. Third, and most politically delicate, the question of who pays for consolidated storage infrastructure has to be resolved between cantonal and municipal budget lines.

Residents with an interest in accessing Zurich's digitised heritage can monitor progress through the Stadtarchiv's public consultation process, which is accepting submissions through its website on Alfred-Escher-Strasse. The next public reporting milestone is set for the fourth quarter of 2026.