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Good practice Imported

Nantes Métropole's Public Algorithm Registry — France's First Open-Sourced Municipal Algorithms

France · Nantes · See the France profile

Evidence: Descriptive / self-reported Top 62% 53/100 · Ask Evidence Copilot about this practice

Nantes Métropole became the first French metropolitan authority to publish the source code of algorithms it uses — water and transport low-income tariff calculators — fulfilling a 2019 data-charter pledge and a July 2020 legal transparency duty.

2 algorithms
Algorithms published as open source (October 2020)
Nantes Métropole's Public Algorithm Registry — France's First Open-Sourced Municipal Algorithms

Details

Maturity
Scaling
Promoter
Nantes Métropole
Period
2019–2025 (ongoing)
Region (NUTS)
FRG01
Keywords
digital government, open data, algorithmic transparency, local government

Context

Nantes Métropole became the first French metropolitan authority to publish algorithm source code, releasing the code for its water and transport low-income tariff calculators on its own open-data portal (data.nantesmetropole.fr) on 6 October 2020.

Objectives

The publication fulfilled commitments from Nantes Métropole's June 2019 data charter and the national Digital Republic Law's transparency requirement (Code des relations entre le public et l'administration, art. L.312-1-3), which took effect 1 July 2020 and mandates disclosure of automated systems used in administrative decisions, following guidance from Etalab, France's open-data and algorithm-transparency unit.

Activities

Two algorithms were published as open source in October 2020; in 2025 the initiative was extended into an updated Metropolitan Data & AI Charter adding AI-specific commitments, including bans on biometric identification and a requirement to compare AI systems against non-AI alternatives.

Results

The registry has not been confirmed to have grown beyond the original two published algorithms, and no measured downstream effects on citizen trust or administrative appeals were reported.

Conclusions

Nantes Métropole's registry operationalises France's national algorithm-transparency law at municipal level and has evolved into a broader AI charter, but its impact remains undemonstrated beyond the initial two-algorithm publication.

Implementation
Indicative cost
Low (< €50k) — Low incremental cost — publishing existing algorithm source code on an existing open-data portal.
Time to results
Short (< 1 year) — June 2019 charter commitment to October 2020 publication (~16 months); expanded into a broader Data & AI Charter in 2025.
Staffing & skills
Nantes Métropole digital/open-data team, Etalab (national open-data/algorithm-transparency unit) guidance

Conditions for success

  • existing open-data portal infrastructure (data.nantesmetropole.fr)
  • national legal mandate (Digital Republic Law, art. L.312-1-3) creating a baseline obligation
  • prior public data-charter commitment (June 2019) establishing political buy-in

Common failure modes

  • no confirmed growth beyond the original two published algorithms
  • no measured downstream effect on citizen trust or administrative appeals

Where it fits

Governance type
metropolitan/municipal government (Nantes Métropole)
Scale
single French metropolitan authority
Income level
high-income (EU member state)

Commonly funded by

National / regional programmes Own resources / municipal budget

Indicative funding routes for practices of this type — always check each programme's current calls and eligibility rules.

Replication kit

Reusable artefacts from this practice — as published by their sources.

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Data sources

Where this practice's information was retrieved from, and when.

Attachments

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