Copenhagen's Digital Archives Are Riddled With Duplicate Images — and Officials Are Finally Talking About It

Copenhagen's municipal digital infrastructure holds tens of thousands of duplicate images across its planning, heritage, and communications databases — and the problem has grown serious enough that the City of Copenhagen's Technical and Environmental Administration has flagged it as a priority for its 2026–2027 digitalisation review cycle.

The issue matters now because the city is mid-way through a major push to digitise building permits, neighbourhood planning documents, and cultural heritage records. Redundant image files slow database queries, inflate storage costs, and — most critically — create confusion when outdated photographs of buildings or streetscapes are used in planning applications instead of current ones. With Nørrebro's Superkilen park undergoing a secondary infrastructure review and the ongoing redevelopment around Carlsberg Byen in Vesterbro, planners say the risk of acting on wrong visual data is not hypothetical.

The Copenhagen City Archive, located on Jagtvej in Nørrebro, manages historical photographic records going back to the 19th century. Staff there have reported that the digitisation programme launched under the 2022–2025 Digital Copenhagen Strategy inadvertently imported multiple versions of the same image files when migrating from older systems. Some individual building records now contain up to a dozen near-identical photographs, differing only in file metadata.

What Experts Are Saying

Urban data specialists at the IT University of Copenhagen on Rued Langgaards Vej have been studying the problem as part of a broader research project on municipal data quality. Their preliminary findings, presented at a May 2026 seminar at the Copenhagen Business School in Frederiksberg, suggested that duplicate image content can account for a significant share of storage overhead in mid-sized European city archives — a finding consistent with patterns documented in comparable digitalisation programmes in Amsterdam and Vienna.

Heritage organisations are particularly vocal. The Danish Architecture Centre, based at BLOX on Bryghuspladsen in central Copenhagen, has argued that inaccurate or duplicated visual records pose a real risk to the integrity of heritage assessments for listed buildings in areas like Indre By and along Strandgade in Christianshavn. When planners pull image records to assess whether a proposed alteration is consistent with a building's historical appearance, a duplicated or mislabelled photograph can send an assessment in the wrong direction.

The City of Copenhagen's own 2025 annual digitalisation report — published in February 2026 — acknowledged that storage costs for municipal digital records had risen by roughly 18 percent year-on-year, though it did not attribute that increase solely to duplicate content. The report did call for an audit of image repositories across all city departments before the end of the third quarter of 2026.

The Path Forward

The Technical and Environmental Administration has indicated it intends to deploy automated deduplication software across its primary planning database by September 2026. The tool, procured through the city's existing framework agreement with a Nordic IT services supplier, will flag duplicate image files for human review rather than deleting them automatically — a safeguard insisted upon by archivists who note that what appears to be a duplicate sometimes documents a building at two different points in time.

The Copenhagen City Archive has separately proposed a working group that would bring together staff from the archive, the Planning Department at Nørreport, and the Heritage Agency of Denmark to agree on shared metadata standards. Without common standards, deduplication software can miss duplicates that are stored under different file names or in different formats.

For residents and businesses involved in planning applications — particularly those in heritage-sensitive neighbourhoods like Frederiksstaden or along the Amager Strandpark waterfront — the practical advice from city officials is straightforward: always submit new, dated photographs with any planning application rather than relying on images already held in the city's records. Until the audit and deduplication work is complete, the accuracy of the existing image stock cannot be guaranteed.

The audit deadline of Q3 2026 gives the city roughly three months to get a handle on the scale of the problem. Whether the September deduplication rollout holds to schedule will be the first real test of whether Copenhagen's digitalisation ambitions can keep pace with the data mess those ambitions have, in part, created.