Sustainability signals in Turkish HEIs: a content and XAI analysis of university websites

Purpose This study aims to examine sustainability signalling among Turkish higher education institutions (HEIs) included in the 2024 UI GreenMetric (UIGM) World University Rankings. Drawing on institutional and signalling theory, the study investigates the prevalence of digital sustainability signals, their variation across ranking tiers and the relationship between education and research (ED)-related signals and UIGM ED performance scores. Design/methodology/approach A mixed-methods design combining website-based content analysis with explainable artificial intelligence (XAI) was used. Sustainability signalling was measured using 11 Web-based indicators across a stratified sample of 60 universities. Descriptive analysis and tier-based comparisons were conducted to identify institutional patterns. A Random Forest model with SHAP-based explanations was used to explore ranking-related signalling dynamics, while correlation analysis was undertaken to examine associations between ED-related signals and UIGM ED scores. Findings Results show that sustainability signalling is widespread but unevenly institutionalised across Turkish universities. Highly visible, stakeholder-oriented signals are common, whereas more formalised digital signals are less consistently adopted. Tier-based comparisons suggest that higher-ranked universities embed sustainability more deeply, whereas middle-ranked institutions place greater emphasis on academic outputs and reporting. No significant correlation emerges between ED scores and ED-related signals, suggesting a possible loose coupling between digital signalling practices and performance. Practical implications This study highlights that sustainability signalling should be treated as more than a routine communication activity and considered within broader digital environmental governance processes. Universities can enhance credibility by strengthening coordination, transparency and signal-performance alignment. The proposed Sustainability Signalling Framework for Environmental Governance (SSF-EG) provides a practical roadmap to support this integration. Originality/value This study contributes to the literature by theorising sustainability signalling in higher education through the integrated lens of institutional and signalling theory. By combining website-based content analysis with XAI, it offers a novel approach to examining how digital signalling, institutional legitimacy and environmental governance intersect. It further reveals how sustainability signals vary across ranking tiers, examines their limited association with performance outcomes and proposes the SSF-EG for HEIs.