Barcelona Takes Aim at Duplicate Images Clogging Its Digital Heritage Archives — and It's Ahead of Most European Cities

Barcelona's Institut de Cultura de Barcelona, the municipal body overseeing the city's public cultural infrastructure, has begun a systematic audit of its digital image repositories — a direct response to findings that duplicate and near-duplicate photographs account for a substantial share of server load across the city's interconnected archive systems. The audit, which covers holdings at the Arxiu Fotogràfic de Barcelona on Plaça de Pons i Clerch and the Biblioteca de Catalunya on Carrer de l'Hospital, formally got underway in the first quarter of 2026.

The timing is not accidental. Municipal digitisation budgets across Europe expanded sharply after 2020, when pandemic-era closures forced institutions to accelerate online access. That rush produced results — more collections accessible from home screens — but also a secondary headache: rushed ingestion workflows that failed to catch redundant files. Barcelona is now paying a housekeeping bill that faster-moving cities like Amsterdam and Vienna are also beginning to receive, but which many others, including Lisbon and Warsaw, have yet to fully reckon with.

The Scale of the Problem in Barcelona's Own Archives

The Arxiu Fotogràfic de Barcelona holds more than four million images spanning the late nineteenth century through to the present. Archive staff and technicians working under the 2025–2028 Pla de Digitalització approved by the Ajuntament de Barcelona have identified that certain historical collections — particularly photographs from the 1936–1939 period and the post-Franco urban renewal documentation from the Eixample district — exist in multiple scanned versions of varying resolution, donated separately by different institutions over successive digitisation cycles. Storage duplication at that scale translates directly into retrieval inefficiency and inflated cloud licensing costs.

The city is running a perceptual hashing protocol — software that generates a fingerprint for each image based on visual content rather than file name or metadata — to flag matches across repositories. Similar tools have been deployed by the Europeana network, the EU-backed aggregator that draws on collections from more than 3,000 institutions across 41 countries. Europeana's own published guidance from 2023 estimated that duplicate or near-duplicate records in aggregated digital collections can run as high as 12 percent of total holdings, a figure that technical teams in Barcelona say is broadly consistent with what they are encountering in their preliminary scans.

How Barcelona Compares With Amsterdam and Vienna

Amsterdam's Stadsarchief — the city's municipal archive, headquartered in a converted insurance building on Vijzelstraat — completed a comparable deduplication exercise across its photographic holdings in late 2024. The Dutch institution used a combination of automated hashing and manual curatorial review, a two-track method that Barcelona's team is studying. Vienna's Wienbibliothek im Rathaus began similar work in early 2025, working within the Austrian national framework for digital preservation standards set by the Österreichische Nationalbibliothek.

Barcelona's approach differs in one meaningful respect: the city is linking its deduplication effort directly to its broader short-term rental and housing data infrastructure upgrade. The Ajuntament under Mayor Jaume Collboni has been expanding digital governance tools since 2023, and archivists are drawing on the same vendor contracts already in place for municipal data management — a cross-departmental efficiency that Amsterdam and Vienna have not yet replicated at scale. Whether that integration speeds delivery or introduces bureaucratic friction will become clearer by the end of 2026, which is the target date for completing the first phase of the audit.

For researchers and journalists who rely on the Arxiu Fotogràfic's public interface, the practical upshot is that search results should become cleaner and faster once duplicate records are collapsed into single canonical entries with version notes attached. The Biblioteca de Catalunya has said it expects to publish updated metadata standards for image submissions from partner institutions by autumn 2026, which would prevent the problem from recurring as new donations arrive. Institutions with holdings they plan to donate are being encouraged to contact the archive's ingestion team before the standards document is finalised, to ensure their files meet the new requirements from the outset.