Barcelona's Duplicate Image Problem: The Numbers That Are Costing the City's Digital Archives Millions

Barcelona's municipal digital archive holds more than 4.2 million image files — and city technicians estimate that close to 18 percent of them are exact or near-exact duplicates. That single inefficiency, uncorrected across several years of rapid digitisation, has translated into wasted server capacity running to tens of thousands of euros annually, according to budget documentation reviewed by The Daily Barcelona.

The issue has moved from a back-office headache to a pressing line item in 2026 because Mayor Jaume Collboni's administration committed in its 2025 municipal technology plan to consolidating Barcelona's fragmented digital infrastructure before the end of this legislative term. That deadline is now roughly 18 months away, and the duplicate-image backlog stands as one of the largest unresolved tasks inside the Arxiu Municipal Contemporani de Barcelona, housed on Carrer de Salvador Espriu in the Vila Olímpica district.

How the Duplication Crisis Grew

The problem did not appear overnight. Between 2018 and 2024, at least four separate digitisation drives ran in parallel — one focused on architectural permits in the Eixample, another cataloguing street-level photography from Gràcia and Sant Pere, a third ingesting legacy press images from the now-restructured Barcelona Cultura agency, and a fourth handling real-estate documentation tied to the city's short-term rental enforcement programme. Each project used different file-naming conventions and metadata standards. Nobody ran a systematic deduplication check between them.

The result: the same photograph of a Gaudí façade on Passeig de Gràcia can appear under three separate catalogue entries, each consuming roughly 22 megabytes of archival-grade TIFF storage. Multiply that across tens of thousands of overlapping heritage images and the storage bill compounds fast. Industry benchmarks used by European municipal archives suggest that unmanaged duplication rates above 15 percent typically add between 12 and 20 percent to annual storage operating costs. Barcelona's own internal audit, circulated to the Comissió de Presidència i Pressupost in March 2026, placed the excess cost at approximately €340,000 over the past three fiscal years combined.

The audit also found that duplicates slow retrieval times for journalists, researchers and civil servants querying the archive through the open-data portal at opendata-ajuntament.barcelona.cat. Average query response times for image-heavy searches had crept up to 4.7 seconds by the fourth quarter of 2025, against a service-level target of under 2 seconds set when the portal was relaunched in 2022.

What the City Plans to Do About It

The Ajuntament de Barcelona signed a framework contract in May 2026 with a consortium of local technology firms to deploy perceptual-hashing deduplication software across the archive. Perceptual hashing identifies visually identical or near-identical images even when file names differ — a critical capability given the inconsistent naming across the four historic digitisation projects.

The contract, valued at €185,000 over 18 months, covers the Arxiu Municipal Contemporani and extends to the photographic collections held at the Arxiu Fotogràfic de Barcelona on Plaça de Pons i Clerch in the Sant Pere neighbourhood. Technicians expect the first full deduplication pass to be complete by the end of October 2026, with a projected reduction of around 750,000 redundant files. If the audit's estimates hold, that should bring annual storage costs down by roughly €90,000 per year going forward.

The process carries its own risks. Automated deduplication tools occasionally flag images as identical when subtle archival differences — a different print date, a distinct negative number stamped on the reverse of a photograph — actually make both versions worth keeping. The city's archivists plan to apply a manual review layer to any file flagged in collections predating 1980, where metadata is thinnest and errors most costly.

For anyone who uses the open-data portal regularly — local historians, architects pulling permit precedents, journalists researching the Eixample's urban evolution — the practical payoff should be faster searches and a cleaner, more reliable catalogue. The city has set a public progress dashboard to go live at the opendata portal in September 2026, so users can track how many duplicates have been resolved month by month. That kind of transparency is rare in municipal IT projects, and it will make it harder to let the deadline quietly slip.