Copenhagen's Duplicate Image Problem: The Decisions That Will Shape the City's Visual Archive

Copenhagen Municipality is facing a decision point over its sprawling digital image archive — one that has quietly ballooned into a logistical and bureaucratic headache affecting departments from the City Archives on Raadhusstræde to the urban planning offices at Teknik- og Miljøforvaltningen on Islands Brygge. Tens of thousands of duplicate images, accumulated over more than a decade of digitisation projects, now clog shared servers and complicate access to the city's official visual record.

The issue has moved up the agenda in part because Copenhagen's ongoing push to digitise historical records — accelerated since 2022 under the municipality's Digital Strategy framework — has created overlapping workflows. Different departments independently scanned and uploaded materials without a unified deduplication protocol. The result is a fragmented archive where the same photograph of, say, Nørreport Station under construction can appear in four separate folders under four different metadata tags, none of them cross-referenced.

What the Problem Actually Costs

Storage is not cheap. The municipality's IT procurement records, reviewed as part of public budget reporting, indicate that cloud and server infrastructure for municipal data sits within a contract framework renewed in early 2025. Industry benchmarks suggest that unmanaged digital duplication can inflate storage costs by 20 to 40 percent in large public-sector archives — though the municipality has not published a Copenhagen-specific figure. What is clear from internal reporting discussed at Borgerrepræsentationen committee meetings this spring is that the archive rationalisation project has been assigned a working budget line for 2026, with a review milestone expected before the end of Q3.

Stadsarkivet — the City Archives — has been designated the lead body for resolving the duplicate image question. Staff there have been piloting automated deduplication software since February, testing it against a subset of images from the Østerbro district documentation project, which spans roughly 14,000 photographs taken between 1998 and 2019. Early results from the pilot identified duplication rates above 30 percent in certain collection batches.

The practical stakes extend beyond tidiness. When journalists, researchers, or citizens submit access requests under the Danish Public Records Act — Offentlighedsloven — duplicate entries slow processing times and occasionally produce conflicting metadata that makes it unclear which version of an image is the authoritative record. Schools using the archive for local history projects, including several linked to the Grundtvig adult education network in Nørrebro, have flagged the confusion in feedback forms submitted to Stadsarkivet.

The Decisions Ahead

Three choices will define what happens next. First, the municipality must decide whether to adopt a fully automated deduplication process or retain manual curatorial oversight for historically sensitive material — a distinction that matters enormously for images tied to politically charged periods in the city's past, such as the 1993 Nørrebro riots documentation held in the archive. Automated tools can misidentify near-duplicate images — slightly different exposures or crop variations — as identical, potentially discarding images that carry distinct evidentiary value.

Second, Teknik- og Miljøforvaltningen and Stadsarkivet will need to agree on a shared metadata standard before any mass deletion takes place. Without that agreement, a clean-up of duplicates in one department's system could strand orphaned references in another's. Talks between the two bodies are scheduled for September, according to the Q3 timeline referenced in committee documentation.

Third, and most politically delicate, is the question of public consultation. Copenhagen's 2025 Digital Strategy committed the municipality to transparency in data governance. Civil society groups, including the Danish chapter of the Open Knowledge Foundation, have previously argued that any large-scale deletion of public records — even ostensible duplicates — should carry a formal review period allowing researchers to flag items before removal.

The September deadline is not fixed in stone, but slipping past it would push the decision into budget season, when political attention shifts to the 2027 municipal spending round. Stadsarkivet staff are understood to be preparing a recommendation paper for the Culture and Leisure Committee by late August. Residents with specific concerns about particular collections can submit written input directly to Stadsarkivet at Raadhusstræde 11 — a process that has been open since June and closes on August 15.