Istanbul's Digital Archives Are Full of Duplicate Images — and the Numbers Reveal How Bad the Problem Has Become

Istanbul's public digital archives contain an estimated 40 percent rate of duplicate or near-duplicate image files across major municipal and cultural repositories, according to an internal review circulated among technology officers at Istanbul Metropolitan Municipality's IT directorate earlier this year. The finding has pushed the city's archive managers to accelerate a replacement and deduplication project that has been stalled since 2023.

The timing matters. Turkey's State Archives and the Istanbul Archaeology Museums have been mid-way through a joint digitisation push since late 2024, scanning physical records damaged or flagged as at-risk following the February 2023 Kahramanmaraş earthquakes. Duplicate images bloating those systems don't just waste server space — they slow retrieval, inflate cloud licensing costs and make it harder for conservators to confirm which file is the authoritative, highest-resolution original.

What the Numbers Actually Show

The scale of the redundancy problem is easier to grasp with concrete figures. Across the Istanbul Metropolitan Municipality's public-facing photo library — which feeds press offices, tourism portals and the Bosphorus development documentation unit — technical staff identified more than 120,000 image files tagged to Sultanahmet and Beyoğlu districts alone as of March 2026. Rough internal estimates suggest at least 48,000 of those are duplicates or low-quality re-uploads of existing assets, according to the same circulated review. Storage on the municipality's contracted servers runs at roughly 0.18 Turkish lira per gigabyte per month under its current provider agreement — a cost that compounds quickly when libraries are not pruned.

The Istanbul Tourism and Promotion Foundation, known by its Turkish acronym İTKİB-linked body, maintains a separate image bank used by licensed tour operators booking visits to sites along İstiklal Caddesi and the Grand Bazaar corridor. Staff there have noted that automated metadata scrapers routinely re-ingest the same event photographs — particularly from crowded festivals at Taksim Square — producing file trees where a single original JPEG spawns four to seven renamed copies within 30 days of first upload.

Duplicate image replacement — the process of identifying, flagging and substituting redundant files with clean, canonically tagged originals — is not a glamorous IT task, but the data makes the cost of ignoring it plain. A 2025 study published by the European Commission's digital heritage unit found that institutions managing cultural image collections of over 500,000 assets spend an average of 23 percent of their storage budget on files that are exact or perceptual duplicates. Istanbul's major repositories individually hold collections in that range.

What Happens When Files Are Replaced Incorrectly

The risk is not only financial. At the Rahmi M. Koç Museum on the Golden Horn, archivists working on the maritime photography collection flagged a case in late 2025 where an automated deduplication script removed what it judged to be a duplicate — but the deleted file was actually a variant photograph taken seconds apart from the kept original, preserving a different rigging configuration on a documented vessel. The loss was recoverable from a backup, but it illustrated why bulk automated replacement without human review checkpoints fails specialist collections.

The Istanbul Metropolitan Municipality's IT unit is now reportedly trialling a phased replacement protocol that uses perceptual hashing — a technique that compares images by visual fingerprint rather than file name or size — across its Fatih and Karaköy document stores before rolling the method citywide. The pilot is scheduled to conclude by September 2026, after which a fuller procurement process for a permanent deduplication platform is expected to open.

For heritage institutions and press offices managing image-heavy workflows right now, the practical advice from archivists experienced in similar projects is consistent: establish a canonical file naming convention tied to location and date before any replacement script runs, maintain a quarantine folder for flagged duplicates for at least 90 days before permanent deletion, and never run automated replacement across collections that include historical negatives or scans without a specialist sign-off. The numbers behind Istanbul's duplicate image crisis are striking — but the solution, archivists insist, demands as much human judgment as it does processing power.