Prague's Digital Archives Are Drowning in Duplicate Images — Here's What the Numbers Reveal

Prague's municipal digital infrastructure holds an estimated 4.2 million image files across city department servers — and according to an internal audit completed in May 2026 by the Prague City Hall IT directorate, as many as 38 percent of those files are exact or near-exact duplicates. That single figure — roughly 1.6 million redundant image files — is now driving an emergency data-cleansing programme that city administrators say will run through the end of the year.

The timing matters. Prague is mid-way through its Smart City Prague 2030 strategy, which commits the municipality to full digitisation of planning, property, and heritage records. The Magistrát — Prague's central city administration building on Mariánské náměstí — has been scanning physical documents since 2019, but the deduplication problem suggests that speed came at the cost of quality control. Every duplicate stored costs money: commercial cloud storage rates for Czech public institutions currently run between 0.80 and 1.20 CZK per gigabyte per month under standard government framework contracts.

Where the Bloat Is Worst

The audit identified three departments generating the heaviest duplicate loads. The Heritage Conservation Department, which manages records for Prague's UNESCO-listed historic centre, accounted for 22 percent of all duplicates — largely because the same architectural photographs were uploaded separately by multiple staff members over several years. The Department of Urban Development and Spatial Planning, responsible for projects from Karlín to Smíchov, contributed another 18 percent. A third significant source was the Prague 1 district office, which scanned large batches of property boundary maps in 2022 without running deduplication checks first.

Prague's Institute of Planning and Development — known by its Czech acronym IPR Praha, based on Vyšehradská street — flagged the problem to the Magistrát in late 2025 after its own geospatial image library ballooned to over 900 gigabytes despite covering a relatively stable dataset. Cross-referencing showed that 41 percent of files in that specific library were duplicates, with some images appearing as many as seven times under different file names.

The financial exposure is not trivial. If the city is storing an excess 600 gigabytes of duplicate image data — a conservative estimate based on the audit's summary figures — and paying toward the upper end of the framework rate, the annual waste approaches 8,640 CZK per year for that slice alone. Scaled across all departments and factoring in backup redundancy layers, which typically multiply storage costs by a factor of three, the real figure likely runs into the hundreds of thousands of crowns annually.

The Technical Fix — and What Comes Next

The city has contracted the deduplication work under an existing IT services agreement with a Central Bohemian Region procurement body, rather than issuing a new public tender. Automated hash-matching software — which generates a unique fingerprint for each image file and flags identical copies — is being deployed in phases. Phase one, covering the Heritage Conservation Department, began on 2 June 2026. Phase two, targeting IPR Praha's geospatial library and the Urban Development archives, is scheduled for September.

The programme also touches residents more directly than they might expect. Prague's online building permit portal, which received more than 47,000 applications in 2025 according to city data released earlier this year, relies on the same backend image infrastructure. Slow retrieval times — partly caused by bloated directories — have been a recurring complaint from architects and developers working on projects from Holešovice to Žižkov. Faster, cleaner records should cut average document retrieval times, though the city has not yet published a target benchmark.

For anyone interacting with city planning offices, the practical advice is to check submission guidelines carefully. The Magistrát now requires unique file naming conventions for all image uploads via the eGovernment portal — a rule introduced on 1 January 2026 that should reduce new duplicate creation going forward, even as technicians clean up the existing backlog. Whether the September phase two deadline holds will depend on how cleanly the automated tools handle near-duplicates — files that are visually identical but differ by a single pixel or metadata tag — which the audit noted represent roughly 12 percent of the duplicate pool and require manual review.