How Stockholm's Public Archive Ended Up Drowning in Duplicate Images — and What It's Doing About It

Stockholm's municipal archive holds tens of thousands of photographs — street scenes from Södermalm, construction records from the Norra Djurgårdsstaden development zone, planning documents from Östermalm going back decades. The problem is that a significant portion of those files appear more than once, sometimes three or four times, under different file names, in different departmental folders, catalogued by different teams who had no way of knowing the image already existed somewhere else in the system.

The issue did not emerge overnight. It is the accumulated result of roughly fifteen years of piecemeal digitisation work, during which individual city departments — the stadsbyggnadskontoret, or City Planning Office, the cultural heritage body Stockholms stadsmuseum, and the city communications unit at Stadshuset — each built their own image repositories with their own naming conventions and their own metadata standards. When administrators began work in early 2025 on consolidating these into a unified digital asset management platform, they discovered the scale of the duplication problem for the first time in full.

How the Fragments Piled Up

The roots of the problem trace to the mid-2000s, when the City of Stockholm began digitising physical photo archives in earnest. Each department received its own budget allocation and its own vendor contracts. Stadsbyggnadskontoret scanned construction permits and site photographs. Stadsmuseum digitised its historical collection, which included images of Gamla Stan, the Slussen redevelopment area, and the old Katarina elevator before its 2016 closure for renovation. The communications unit maintained a separate library of press-ready images for media use.

None of these systems talked to one another. A photograph taken at the Slussen construction site in 2014, for example, might have been filed by three separate departments for three separate purposes, each scan slightly different in resolution or cropping. Multiply that across thousands of construction projects, public events, and planning consultations over fifteen years, and the redundancy compounds rapidly.

By the time the consolidation project began formally under the city's Digitaliseringsprogram 2024–2026 framework, internal assessments — described in city council budget documents from November 2024 — put the total image library across all departments at approximately 340,000 files. Early-stage auditing suggested that between 25 and 35 percent of those files were functional duplicates or near-duplicates, meaning the city was storing and maintaining somewhere between 85,000 and 120,000 redundant image files at an estimated storage and licensing overhead running into several hundred thousand kronor annually.

What Comes Next for the Archive

The practical work of removing duplicates is more complicated than simply running a hash-check across the file system. Many images were re-scanned at different resolutions for different purposes, meaning they are not technically identical even when they depict the same subject. The city's IT department, working with the procurement unit at Rådhuset, brought in a specialist image-deduplication workflow in the spring of 2026 that uses perceptual hashing — a method that compares images based on visual content rather than file data — to flag likely matches for human review.

As of July 2026, the review team has processed roughly 40 percent of the flagged files. The project is scheduled for completion before the end of the third quarter, ahead of the planned public launch of a unified Stockholms stadsarkiv image portal. That portal, when it opens, is intended to give journalists, researchers, and residents a single search point for city-held images, replacing the current situation in which finding a photograph of, say, the 1967 demolitions in Klara requires knowing which departmental archive to approach.

For residents or local organisations who regularly request images from the city for heritage or planning purposes, the practical advice for now is to continue using the existing departmental contact points — stadsmuseum for historical material, stadsbyggnadskontoret for planning photography — and to expect consolidated access through the new portal sometime in September or October 2026. The city has said the new system will carry a Creative Commons licensing framework for non-commercial use, which would mark a significant change from the current arrangement under which image rights are handled separately by each department.