Zürich's Digital Archive Crisis: The Hidden Scale of Duplicate Image Sprawl

Zürich's public institutions are sitting on a quietly ballooning problem: duplicate images. Internal audits and procurement records reviewed by The Daily Zurich show that municipal data centres, university archives, and cantonal administration systems collectively store tens of millions of redundant image files — identical or near-identical photographs, scans, and graphics saved multiple times across overlapping servers. The cost of that redundancy, measured in storage fees, licensing overhead, and IT labour, now runs into the millions of francs per year.

The timing matters. The city is in the middle of a multi-year push to digitise cantonal records and modernise the administration under its Smart City Zürich programme, which the city council formally extended through 2028. Every redundant file that migrates from an old server to a new cloud environment costs money twice — once to store it, and again to audit it later. For a city already navigating a strained housing budget and the ongoing structural adjustments demanded by the post-Credit Suisse financial landscape, administrative waste in digital infrastructure is drawing fresh scrutiny.

What the Numbers Actually Show

ETH Zürich's IT services division, one of the largest institutional data operators in the canton, estimates that between 20 and 35 percent of image assets stored in typical academic and administrative repositories are exact or near-exact duplicates. Applied to the university's publicly reported research data storage footprint, which exceeded 4.2 petabytes as of its 2024 annual report, even a conservative deduplication pass could theoretically recover hundreds of terabytes of capacity. At current commercial cloud storage rates — roughly CHF 20 to CHF 25 per terabyte per month for enterprise-grade Swiss-hosted infrastructure — the arithmetic becomes uncomfortable fast.

The City of Zürich's own Stadtarchiv, located on Neumarkt in the Altstadt, has digitised more than 1.2 million historical images and documents since launching its digitisation programme in 2018. Archivists there have publicly acknowledged that early batch-scanning processes produced significant duplication, particularly for series of photographs taken in rapid succession. Zürich's Stadtarchiv is now piloting perceptual hashing software — a technique that identifies visually similar images even when file metadata differs — to flag and reclassify redundant assets before they are migrated to the canton's consolidated cloud infrastructure later this year.

The Zentralbibliothek Zürich, on Zähringerplatz, faces a parallel challenge. Its digitised newspaper and photograph collections run to several million files, and the library's 2025 digitisation strategy report noted that duplicate detection had not been systematically integrated into earlier scanning workflows. Staff estimate that manual deduplication of legacy collections would require the equivalent of roughly 1.5 full-time positions over two years — a cost the library is hoping to offset through automation grants from the Swiss National Science Foundation.

What Institutions Are Doing About It

Automated deduplication tools have matured considerably. Software that cross-references file hashes and pixel-level similarity scores can process a terabyte of image data in under four hours on standard server hardware. Several Zürich-based technology firms operating out of the Technopark Zürich on Technoparkstrasse have developed Swiss-hosted solutions marketed specifically at GDPR- and nDSG-compliant institutions that cannot push sensitive archival material to foreign cloud providers.

The cantonal government's Amt für Informatik has reportedly included duplicate-image-detection requirements in its 2026 framework contract for cloud migration services, though the full tender specifications had not been published as of this writing. That requirement, if enforced, would represent the first time deduplication is mandated rather than merely recommended across cantonal IT procurement.

For institutions that have not yet acted, the practical advice from IT governance specialists is consistent: run a baseline audit before any cloud migration, not after. Migrating duplicates and then paying to store and index them in a new environment is substantially more expensive than catching them on-premises first. In Zürich's case, with the canton's consolidated cloud contract expected to go live in phases from late 2026, the window for cheap remediation is narrowing. Institutions that delay past the migration deadlines will inherit the costs — and the clutter — for years.