Synthetic organic tanning agents (syntans) are engineered to mimic or replace traditional tanning substances such as chromium salts. They enable precise control over leather softness, color, and fullness while reducing dependency on metal-based systems. These agents are often used in wet-white tanning, re-tanning, and as fillers or dispersants during drum processing. From a sustainability perspective, syntans eliminate heavy metal discharge, reduce COD in wastewater, and support the production of biodegradable and hypoallergenic leathers. Many are formaldehyde-free and designed to meet rigorous chemical safety standards. Ongoing research is focused on enhancing the bio-based content of syntans, improving their penetration and exhaustion, and enabling better integration with low-salt or chrome-free pre-tanning systems. Responsible sourcing through B2B marketplaces enables tanneries to find high-performance syntans tailored for specific leather types and aligned with traceability and environmental objectives.