IX rolls up behavioural signals (time on site, bounces, return-to-SERP), commercial signals (for e-commerce), accessibility, content quality, and links. Low IX doesn't block ranking but caps it. You can't raise IX directly — it grows when the site actually becomes better.
Yandex IX (ICS)
IX (Site Quality Index, sometimes ICS) — Yandex's public 0-to-∞ metric reflecting the site's usefulness in Yandex's view.