Copenhagen's Municipal Archive Launches Emergency Audit After Duplicate Image Crisis Surfaces in Digital Records

Copenhagen's municipal digital archive has been wrestling this week with a significant data integrity problem: hundreds of duplicate images embedded in public planning and permit records, some appearing as many as four times under different file names, are distorting the city's official property database and slowing down decisions at the Teknik- og Miljøforvaltningen, the city's technical and environmental administration based on Njalsgade.

The issue surfaced publicly on Monday, 29 June, when residents using the online Byg og Miljø portal — the primary self-service system Copenhageners use to check building permits, zoning changes and neighbourhood development plans — reported that image attachments on planning cases in the Østerbro and Nørrebro districts were either missing, doubled, or displaying photographs belonging to entirely different properties. By Wednesday, the administration had confirmed the scope extended to records filed as far back as 2019.

Why the Timing Is Particularly Awkward

The discovery lands at a difficult moment for the city's urban development apparatus. Copenhagen is currently processing a higher-than-usual volume of permit applications connected to the densification strategy around the Sydhavn area and the ongoing construction corridor running along Amager Fælledvej. Delays in verifying photographic documentation — which planners rely on to assess existing building conditions — risk pushing decisions past statutory deadlines, which under Danish building law can trigger automatic approvals in certain lower-risk categories.

The root cause, according to internal communications reviewed by The Daily Copenhagen, appears to be a migration error during a platform upgrade carried out in late 2024. When case documents were transferred from the legacy GeoEnviron system to the newer ESDH-integrated platform, image metadata was not properly deduplicated. Instead of each photograph being stored once and referenced across linked cases, the system created fresh copies for every association — a compounding problem as popular reference images, such as street-level shots of listed buildings in the Frederiksstaden conservation zone, were linked to dozens of separate cases.

The Byg og Miljø portal handles roughly 18,000 new building cases per year across Copenhagen's ten districts, and technical staff estimate that approximately 12 percent of cases filed between January 2024 and April 2026 contain at least one duplicate image attachment. That translates to somewhere in the region of 4,300 affected case files, though the administration has not yet published a final count. Correcting each file manually takes between 15 and 45 minutes, depending on complexity.

What the City Is Doing This Week

Teknik- og Miljøforvaltningen confirmed on Thursday that it has assembled a dedicated remediation team of six data administrators working out of the Njalsgade offices to run an automated deduplication script across the archive, followed by manual verification for flagged cases. The script, developed in cooperation with the IT supplier KMD, began running on Tuesday evening and had processed approximately 1,100 files by Friday morning.

The Grundejerforeningen for Indre By — the property owners' association covering the inner city — sent a formal inquiry to the administration on 1 July requesting clarity on whether any active permit decisions had been delayed as a direct result of the image errors. The administration has until 15 July to respond formally under the standard forvaltningsloven inquiry process.

Residents and property owners with pending applications can check whether their specific case is affected by logging into Byg og Miljø using their MitID credentials and looking for a yellow warning banner that the city added to affected case pages on Wednesday. Anyone whose case carries a statutory decision deadline within the next 30 days is being advised to contact the permit centre by telephone — the direct line is listed on the portal — to request a manual review and, if necessary, a documented extension of the decision timeline.

The administration has said it expects the bulk of the automated correction work to be complete by 17 July, with full manual verification of priority cases wrapped up before the summer recess ends in mid-August. Whether the portal will then require a further technical audit to prevent a recurrence of the migration problem is a question the city's IT board is scheduled to take up at its next meeting on 22 July.