Copenhagen's Digital Archive Faces a Reckoning: The Key Decisions Ahead on Duplicate Image Replacement

Copenhagen's municipal cultural agencies are approaching a decision point that will shape how the city's visual history is stored, accessed and presented for years to come. A coordinated review of digitised photographic holdings — spread across institutions including the Copenhagen City Archive on Rådhuspladsen and the Royal Danish Library's collections at Slotsholmen — has identified tens of thousands of duplicate image entries that now require systematic replacement or removal.

The problem has been building since at least 2019, when accelerated digitisation programs brought large volumes of analogue material online quickly. Speed, at the time, mattered more than deduplication. Now the backlog is a practical and financial problem: redundant files consume server capacity, muddy search results, and slow the work of researchers, journalists and city planners who rely on these archives daily.

What the Review Has Uncovered

Duplicate image replacement is not simply a matter of deleting obvious copies. Many duplicates exist because the same physical photograph was scanned at different resolutions, or because multiple institutions digitised the same donated collection independently. The Copenhagen City Archive, which holds records dating to the 1850s, has flagged this overlap as a particular challenge in collections covering Nørrebro and Vesterbro, two neighbourhoods whose urban transformation over the past 40 years is extensively documented in both official and community-donated material.

The practical stakes are significant. When a researcher requests images of, say, Istedgade in 1987 for an urban planning report, a database returning 14 near-identical scans of the same print wastes time and introduces doubt about which version carries the authoritative metadata. Archivists must then manually reconcile records — work that, according to the Danish Agency for Culture and Palaces' 2024 annual sector report, already accounts for a disproportionate share of cataloguing hours across the country's publicly funded archives.

Costs are not trivial. Cloud storage for cultural institutions in Denmark has increased in price considerably since 2022, and the Danish State and University Library's infrastructure consortium — which services multiple Copenhagen institutions — has indicated that rationalising duplicate holdings could free up meaningful capacity without additional capital expenditure in the current budget cycle.

The Decisions That Must Now Be Made

Three questions are sitting unresolved on the desks of archive directors heading into the autumn budget season. First: which institution takes the lead on a unified deduplication protocol? The Copenhagen City Archive and the Royal Danish Library have historically maintained separate workflows, and neither has a formal mandate to override the other's cataloguing decisions. A working group is expected to report to the Ministry of Culture before 1 October 2026, according to the ministry's published consultation calendar.

Second, who validates the replacement image when a low-quality duplicate is retired? Simply picking the highest-resolution scan is not always correct — sometimes an older, lower-resolution file carries unique handwritten annotations on the reverse that were captured in its metadata but not in a later rescan. Archival integrity depends on human sign-off, not algorithmic selection alone. The Danish Association of Professional Archivists has been pushing for a formal review standard since at least 2023.

Third, what happens to images donated by private individuals and neighbourhood associations — material from groups like the Nørrebro Local History Archive on Korsgade — when an institution determines their submission duplicates something already held? There is currently no standardised policy on notifying donors, which creates both legal uncertainty and community relations problems.

The practical path forward will likely involve a phased approach: institutions agree on a common metadata standard by the end of 2026, begin automated flagging of duplicates in the first half of 2027, and reserve final deletion authority for trained archivists rather than batch-processing scripts. Community archives with smaller technical teams will need either direct support funding or a shared-service arrangement with the larger institutions. The Copenhagen City Council's Culture and Leisure Committee has scheduled a preliminary briefing on the issue for September. What gets decided there will set the terms for a process that, once started, will be very difficult to reverse.